Silicon Laboratories SI2493/57/34/15/04 User manual

Rev. 1.3 8/11 Copyright © 2011 by Silicon Laboratories AN93
This information applies to a product under development. Its characteristics and specifications are subject to change without notice.
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Si2493/57/34/15/04 (Revision D) and Si2494/39
Modem Designer’s Guide
1. Introduction
The Si2494/93/57/39/34/15/04 ISOmodem chipset family consists of a 38-pin QFN (Si2494/39) or 24-pin TSSOP
(Si2493/57/34/15/04) or 16-pin SOIC (Si2493/57/34/15/04) low-voltage modem device, and a 16-pin SOIC line-
side DAA device (Si3018/10) connecting directly with the telephone local loop (Tip and Ring). This modem solution
is a complete hardware (controller-based) modem that connects to a host processor through a UART, parallel or
SPI interface. Parallel and EEPROM interfaces are available only on the 38-pin QFN or 24-pin TSSOP package
option. Refer to Table 4, “ISOmodem Capabilities,” on page 10 for available part number, capability and package
combinations. Isolation is provided by Silicon Laboratories’ isolation capacitor technology, which uses high-voltage
capacitors instead of a transformer. This isolation technology complies with global telecommunications standards
including FCC, ETSI ES 203 021, JATE, and all known country-specific requirements.
Additional features include programmable ac/dc termination and ring impedance, on-hook and off-hook intrusion
detection, Caller ID, loop voltage/loop current monitoring, overcurrent detection, ring detection, and the hook-
switch function. All required program and data memory is included in the modem device. When the modem
receives a software or hardware reset, all register settings revert to the default values stored in the on-chip
program memory. The host processor interacts with the modem controller through AT commands used to change
register settings and control modem operation. Country, EMI/EMC, and safety test reports are available from
Silicon Laboratories representatives and distributors.
This application note is intended to supplement the Si2494/39 Revision A, Si2493 Revision D, and the Si2457/34/
15/04 Revision D data sheets. It provides all the hardware and software information necessary to implement a
variety of modem applications, including reference schematics, sample PCB layouts, AT command and register
reference, country configuration tables, programming examples and more. Particular topics of interest can be
easily located through the table of contents or the comprehensive index located at the back of this document.
Figure 1. Functional Block Diagram
UART
Interface
Parallel
Interface
DSP
DAA
Interface
ROM
PLL
Clocking
XTI XTO
CLKOUT
INT
RESET
C1
To Phone
Line
AOUT
Data Bus
Controller
Si3018/10
RXD
TXD
CTS
RTS
DCD
ESC
RI
CS
WR
RD
A0
D0-D7
Program Bus RAM
EEPROM
Interface
EESD
EECLK
EECS
C2
Si3000
Interface
FSYNC
SDO
SDI
MCLK
SPI
Interface
SDI
SDO
SCLK
SS
AOUTb

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TABLE OF CONTENTS
Section Page
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1. Selection Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2. Modem (System-Side) Device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.1. Resetting the Device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.1.1. Reset Sequence. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.1.2. Reset Strapping: General Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.1.3. Reset-Strap Options for 16-Pin SOIC Package . . . . . . . . . . . . . . . . . . . . . . . . 13
2.1.4. Reset-Strap Options for 24-Pin TSSOP Package . . . . . . . . . . . . . . . . . . . . . . 13
2.1.4.1. Reset Strapping Options for TSSOP-24 with UART-Interface. . . . . . . . . 14
2.1.4.2. Reset Strapping Options for TSSOP-24 with Parallel-Interface. . . . . . . . 14
2.1.4.3. Reset Strapping Options for TSSOP with SPI-Interface . . . . . . . . . . . . . 15
2.1.5. Reset Strapping Options for QFN Parts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.1.5.1. Reset Strapping Options for QFN Parts with UART Operation . . . . . . . . 15
2.1.5.2. Reset Strapping Options for QFN Parts with SPI Operation . . . . . . . . . . 16
2.1.5.3. Reset Strapping Options for QFN Parts with Parallel Operation . . . . . . . 16
2.2. System Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2.2.1. Interface Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2.2.2. Interface Signal Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.2.3. UART Interface Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.2.3.1. UART Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.2.3.2. Autobaud . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
2.2.3.3. Flow Control. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
2.2.4. Parallel and SPI Interface Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
2.2.4.1. Hardware Interface Register 0. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
2.2.4.2. Hardware Interface Register 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
2.2.4.3. Parallel Interface Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
2.2.4.4. SPI Interface Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
2.2.4.5. Interface Communication Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
2.3. Isolation Capacitor Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
2.4. Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
2.4.1. Power-Down Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
2.4.2. Wake-on-Ring Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
2.4.3. Sleep Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
2.5. SSI/Voice Mode (24-Pin TSSOP and 38-Pin QFN Only) . . . . . . . . . . . . . . . . . . . . . . 30
2.6. EEPROM Interface (24-Pin TSSOP and 38-Pin QFN Only) . . . . . . . . . . . . . . . . . . . . 31
2.6.1. Supported EEPROM Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
2.6.2. Three-Wire SPI Interface to EEPROM. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
2.6.3. Detailed EEPROM Examples. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
2.6.4. Boot Commands (Custom Defaults). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
2.6.5. AT Command Macros (Customized AT Commands) . . . . . . . . . . . . . . . . . . . . 34
2.6.6. Firmware Upgrades . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
2.6.6.1. Boot Command Example. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

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2.6.6.2. AT Command Macro Example. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
2.6.6.3. Autoloading Firmware Upgrade Example . . . . . . . . . . . . . . . . . . . . . . . . 35
2.6.6.4. Combination Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
3. DAA (Line-Side) Device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
3.1. Hookswitch and DC Termination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
3.2. AC Termination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
3.3. Ringer Impedance and Threshold . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
3.4. Pulse Dialing and Spark Quenching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
3.5. Line Voltage and Loop Current Sensing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
3.6. Legacy-Mode Line Voltage and Loop Current Measurement . . . . . . . . . . . . . . . . . . . 42
3.7. Billing Tone Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
4. Hardware Design Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
4.1. Component Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
4.1.1. Power Supply and Bias Circuitry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
4.1.2. Hookswitch and DC Termination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
4.1.3. Clocks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
4.1.4. Ringer Network. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
4.1.5. Optional Billing-Tone Filter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
4.2. Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
4.3. Bill of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
4.4. Layout Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
4.4.1. ISOmodem Layout Check List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
4.4.2. Module Design and Application Considerations. . . . . . . . . . . . . . . . . . . . . . . . 53
4.4.2.1. Module Design. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
4.4.2.2. Motherboard Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
4.5. Analog Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
4.5.1. Interaction between the AOUT Circuit and the
Required Modem Reset Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
4.5.2. Audio Quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
5. Modem Reference Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
5.1. Controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
5.2. DSP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
5.3. Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
5.4. AT Command Set . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
5.5. Extended AT Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
5.6. S Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
5.7. U Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
5.7.1. U-Register Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
5.7.2. U00–U16 (Dial Tone Detect Filter Registers). . . . . . . . . . . . . . . . . . . . . . . . . . 97
5.7.3. U17–U30 (Busy Tone Detect Filter Registers). . . . . . . . . . . . . . . . . . . . . . . . . 98
5.7.4. U31–U33 (Ringback Cadence Registers) . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
5.7.5. U34–U35 (Dial Tone Timing Register) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
5.7.6. U37–U45 (Pulse Dial Registers). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
5.7.7. U46–U48 (DTMF Dial Registers) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
5.7.8. U49–U4C (Ring Detect Registers) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
5.7.9. U4D (Modem Control Register 1—MOD1). . . . . . . . . . . . . . . . . . . . . . . . . . . 103
5.7.10. U4E (Pre-Dial Delay Time Register). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105

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5.7.11. U4F (Flash Hook Time Register) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
5.7.12. U50–U51 (Loop Current Debouncing Registers) . . . . . . . . . . . . . . . . . . . . . 105
5.7.13. U52 (Transmit Level Register) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
5.7.14. U53 (Modem Control Register 2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
5.7.15. U54 (Calibration Timing Register) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
5.7.16. U62–U66 (DAA Control Registers). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
5.7.17. U67–U6A (International Configuration Registers) . . . . . . . . . . . . . . . . . . . . 108
5.7.18. U6C (Line-Voltage Status Register). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
5.7.19. U6E–U7D (Modem Control and Interface Registers). . . . . . . . . . . . . . . . . . 111
5.7.20. U80 (Transmit Delay for V.22 Fast Connect) . . . . . . . . . . . . . . . . . . . . . . . . 119
5.7.21. U87 (Synchronous Access Mode Configuration Register). . . . . . . . . . . . . . 120
5.7.22. UAA (V.29 Mode Register). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
5.7.23. UIDA Response and Answer Tone Delay Register . . . . . . . . . . . . . . . . . . . 121
5.8. Firmware Upgrades . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
5.8.1. Method 1 (Fastest) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
5.8.2. Method 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
5.8.3. Method 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
5.9. Escape Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
5.9.1. +++ Escape . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
5.9.2. “9th Bit” Escape . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
5.9.3. “Escape Pin” Escape . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
5.10. Data Compression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124
5.11. Error Correction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124
5.12. Wire Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124
5.13. EPOS (Electronic Point of Sale) Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
5.13.1. EPOS Fast Connect. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
5.13.2. EPOS V.29 Fast Connect. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
5.14. Legacy Synchronous DCE Mode/V.80 Synchronous Access Mode . . . . . . . . . . . . 125
5.15. V.80 Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
6. Programming Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
6.1. Quick Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
6.2. Country-Dependent Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
6.2.1. DC Termination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
6.2.2. Country Configuration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134
6.2.2.1. Country Initialization Table. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134
6.2.2.2. Country-Setting Register Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145
6.2.2.3. Special Requirements for India . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146
6.2.2.4. Special Requirements for Serbia and Montenegro . . . . . . . . . . . . . . . . 147
6.2.3. Blacklisting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147
6.3. Caller ID . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148
6.3.1. Force Caller ID Monitor (Always On) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148
6.3.2. Caller ID After Ring Only . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148
6.3.3. UK Caller ID with Wetting Pulse. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148
6.3.4. Japan Caller ID. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148
6.3.5. DTMF Caller ID. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
6.4. SMS Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
6.5. Type II Caller ID/SAS Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151

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6 Rev. 1.3
6.6. Intrusion/Parallel Phone Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161
6.6.1. On-Hook Condition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161
6.6.1.1. Line Not Present/In Use Indication (Method 1—Fixed) . . . . . . . . . . . . . 161
6.6.1.2. Line Not Present/In Use Indication (Method 2—Adaptive). . . . . . . . . . . 162
6.6.2. Off-Hook Condition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162
6.7. Modem-On-Hold . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164
6.7.1. Initiating Modem-On-Hold. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164
6.7.2. Receiving Modem-On-Hold Requests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165
6.8. HDLC: Bit Errors on a Noisy Line . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165
6.9. Overcurrent Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169
6.10. Pulse/Tone Dial Decision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169
6.10.1. Method 1: Multiple Off-Hook Transitions. . . . . . . . . . . . . . . . . . . . . . . . . 169
6.10.2. Method 2: Single Off-Hook Transition . . . . . . . . . . . . . . . . . . . . . . . . . . . 170
6.10.3. Method 3: Adaptive Dialing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170
6.10.4. Automatic Phone-Line Configuration Detection . . . . . . . . . . . . . . . . . . . . . . 170
6.10.5. Line Type Determination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170
6.11. Telephone Voting Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171
6.12. V.92 Quick Connect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171
7. Handset, TAM, and Speakerphone Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173
7.1. Software Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173
7.1.1. AT Command Set. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173
7.1.2. AT+ Extended Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173
7.1.3. <DLE> Commands (DTE-to-DCE) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178
7.1.4. <DLE> Events (DCE-to-DTE). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179
7.1.4.1. Simple Event Reporting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179
7.1.4.2. Complex Event Reporting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181
7.1.5. U Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181
7.2. Voice Reference—Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187
7.3. Si3000 Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
7.3.1. Microphone and Speaker Ports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
7.3.2. Register Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
7.3.3. System Voice Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
7.3.3.1. TAM Hands-Free . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
7.3.3.2. TAM Handset. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
7.3.3.3. Speakerphone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
7.3.3.4. Handset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
7.3.3.5. TAM PSTN. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193
7.4. Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194
7.5. Handset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196
7.5.1. Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196
7.5.2. Handset Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196
7.5.3. Call – Automatic Tone Dial. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198
7.5.4. Call – Manual Off-Hook Tone Dial . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198
7.5.5. Call – Automatic Pulse Dial . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198
7.5.6. Answer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198
7.5.7. Terminate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199

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Rev. 1.3 7
7.5.8. Speakerphone Transition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200
7.6. Telephone Answering Machine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201
7.6.1. Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201
7.6.2. TAM Hands-Free—Idle. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201
7.6.2.1. Record OGM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202
7.6.2.2. Review OGM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203
7.6.2.3. Record Local ICM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203
7.6.2.4. Review ICM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203
7.6.2.5. Speakerphone Transition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203
7.6.2.6. Handset Transition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203
7.6.3. TAM Handset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203
7.6.3.1. Record OGM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203
7.6.3.2. Review OGM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206
7.6.3.3. Record Local ICM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208
7.6.3.4. Review ICM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208
7.6.4. TAM PSTN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208
7.6.4.1. Normal Answer – OGM Playback with ICM Record. . . . . . . . . . . . . . . . 208
7.6.4.2. Interrupted Answer – OGM Playback with DTMF Menu Entry. . . . . . . . 210
7.6.4.3. Speakerphone Transition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212
7.6.4.4. Handset Transition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212
7.7. Speakerphone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212
7.7.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212
7.7.2. Simplex Speakerphone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212
7.7.3. External Microphone/Speaker Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . 213
7.7.3.1. Transmit Gain Calibration—Speakerphone Disabled . . . . . . . . . . . . . . 213
7.7.3.2. Receive Gain Calibration—Speakerphone Disabled . . . . . . . . . . . . . . . 216
7.7.3.3. Speakerphone Calibration—AEC Gain Calibration . . . . . . . . . . . . . . . . 217
7.7.4. Speakerphone Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219
7.7.5. Simplex Speakerphone Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220
7.7.6. Call—Automatic Tone Dial . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221
7.7.7. Call—Manual Off-Hook Tone Dial . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221
7.7.8. Call—Automatic Pulse Dial. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222
7.7.9. Answer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222
7.7.10. Handset Transition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222
7.7.11. Termination. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223
7.8. Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223
7.9. References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223
8. Security Protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224
8.1. Implementing the SIA Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224
8.1.1. Modem-Specific Implementation Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224
8.1.1.1. Listen-In and V-channel Periods (Voice Pass-Through) . . . . . . . . . . . . 224
8.1.1.2. Inserting a V.32bis period (e.g., SIA Level-3 Video Block Support). . . . 224
8.1.1.3. Considerations when Disconnecting the Session . . . . . . . . . . . . . . . . . 225
8.2. Implementing the Ademco® Contact ID Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . 228
8.2.1. Modem Specific Implementation Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229
8.2.1.1. Handshake Tone Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230
8.2.1.2. Session Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230

AN93
8 Rev. 1.3
9. Chinese ePOS SMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234
9.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234
9.2. SMS AT Command Set . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235
9.2.1. SMS User Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236
9.2.2. Procedure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237
9.2.2.1. Example. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237
9.2.2.2. Response 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238
9.2.2.3. Response 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238
9.2.2.4. Response 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238
9.3. Example Session . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239
10. Testing and Diagnostics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242
10.1. Prototype Bring-Up (Si3018/10) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242
10.1.1. Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242
10.1.2. Visual Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242
10.1.3. Basic Troubleshooting Steps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242
10.1.4. Host Interface Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243
10.1.5. Isolation Capacitor Troubleshooting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244
10.1.6. Si3018/10 Troubleshooting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244
10.1.7. Component Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244
10.2. Self Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249
10.3. Board Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250
10.4. Compliance Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252
10.4.1. EMI. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253
10.4.2. Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 254
10.4.3. Surges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 254
10.5. AM-Band Interference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255
10.6. Debugging the DTE interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256
Appendix A—EPOS Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257
VISA II (7E1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257
Recommendation V.80 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 258
The ISOmodem in EPOS Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260
A V.29 FastPOS Sample Program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261
Appendix B—Line Audio Recording . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273
When to Use Audio Recording . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273
Times When Audio Recording May Not Help . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273
Hardware Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273
Audio Playback and Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 279
Examples of Line Impairments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 288
Appendix C—Parallel/SPI Interface Software Implementation . . . . . . . . . . . . . . . . . . . . . 290
Software Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292
Compiler Option: Dot Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299
Modem Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299
Modem Interrupt Service Sample Code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 300
Document Change List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 303
Contact Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 304

AN93
Rev. 1.3 9
1.1. Selection Guide
Tables 1 through 3 list the modulations, protocols, carriers, tones and interface modes supported by the Si2494/39
and Si2493/57/34/15/04 ISOmodem family. The Si2493 supports all modulations and protocols from Bell 103
through V.92. The Si2457 supports all modulations and protocols from Bell 103 through V.90. The Si2434 supports
all modulations and protocols from Bell 103 through V.34. The Si2415 supports all modulations and protocols from
Bell 103 through V.32bis. The Si2404 supports all modulations and protocols from Bell 103 through V.22bis.
Table 1. Modulations
Modulation Data Rates (bps) Modulation Si2494/93 Si2457 Si2439/34 Si2415 Si2404
V.92* 48k, 40k, 32k, 24k PCM 
V.90* 56k, 54.6k, 53.3k, 52k, 50.6k,
49.3k, 48k, 46.6k, 45.3k, 44k,
42.6k, 41.3k, 40k, 38.6k,
37.3k, 36k, 34.6k, 33.3k, 32k,
30.6k, 29.3k, 28k
PCM 
V.34* 33.6k, 31.2k, 28.8k, 26.4k, 24k,
21.6k, 19.2k, 16.8k, 14.4k, 12k,
9600, 7200, 4800, 2400
TCM 
V.32bis* 14.4k, 12k, 9600, 7200, 4800 TCM 
V.32* 9600
9600, 4800 TCM QAM 
V.29FC* 9600 QAM *
V.23 1200 FSK 
V.22bis 2400, 1200 QAM 
V.22 1200 DPSK 
Bell 212A 1200 DPSK 
V.21 300 FSK 
Bell 103 300 FSK 
*Note: With the Si3018 DAA only.
Table 2. Protocols
Protocol*Function Si2494/93 Si2457 Si2439/34 Si2415 Si2404
V.44 Compression 
V.42bis Compression 
V.42 Error Correction 
MNP5 Compression 
MNP2-4 Error Correction 
*Note: The Si2494/93/57/39/34/15/04 family allows any supported protocol combined with any modulation.

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10 Rev. 1.3
Table 3. Carriers and Tones
Specification Transmit Carrier
(Hz) Receive Carrier (Hz) Answer Tone (Hz) Carrier Detect (Acquire/ Release)
V.92 Variable Variable per ITU-T V.92
V.90 Variable Variable per ITU-T V.90
V.34 Variable Variable per ITU-T V.34
V.32bis 1800 1800 2100 per ITU-T V.32bis
V.32 1800 1800 2100 per ITU-T V.32
V.29 1700 1700 per ITU-T V.29
V.22bis, V.22
Originate/answer 1200 2400 2400 1200 2100 –43 dBm/–48 dBm –43 dBm/–48 dBm
V.21
Originate/answer (M/S) 1180/980 1850/1650 1850/1650 1180/980 2100 –43 dBm/–48 dBm –43 dBm/–48 dBm
Bell 212A
Originate/answer 1200 2400 2400 1200 2225 –43 dBm/–48 dBm –43 dBm/–48 dBm
Bell 103
Originate/answer (M/S) 1270/1070 2225/2025 2225/2025 1270/1070 2225 –43 dBm/–48 dBm –43 dBm/–48 dBm
Table 4. ISOmodem Capabilities
Part Numbers Package UART EEPROM SPI Parallel SSI/Voice
Si2493/57/34/15/041SOIC-16 
Si2493/57/34/15/041TSSOP-24 2
Si2494/39 QFN-38 
Notes:
1. Die Revision D or later
2. The EEPROM interface option is available only when the UART or SPI interface is selected.

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Rev. 1.3 11
2. Modem (System-Side) Device
The Si24xx ISOmodem system-side devices contain a controller, a DSP, program memory (ROM), data memory
(RAM), UART, SPI and parallel interfaces, a crystal oscillator, and an isolation capacitor interface. The following
sections describe the reset sequence, the host interface, the isolation interface, low-power modes, SSI/voice mode
and the EEPROM interface.
2.1. Resetting the Device
Reset is required after power-on or brownout conditions (the supply dropping to less than the data sheet minimum).
The supply must be stable throughout the minimum required reset time described here and thereafter. A reset is
also required in order to come out of the power down mode.
Some operational choices, including the crystal oscillator frequency used and the command interface used (e.g.
UART vs SPI), is made during the reset time according to pull-down resistors placed on some modem pins. These
pins are modem output lines, but, during reset, the modem places them into a high-impedance mode with weak
internal pull-ups, then reads the user's strapping choices. It is important that the resultant state changes of these
pins during reset are not misinterpreted by the host.
For example the INT output pin of the modem (and perhaps others) can be strapped low with a 10 kresistor to
request SPI operation. If that mode is chosen, the host should take care not to enable this interrupt input before the
modem reset since the INT signal will transition from high to low and back up during reset in this case and can
generate an unexpected interrupt.
If an external clock signal is provided instead of a crystal attached to the modem, it is important that this external
clock signal be stable before the reset ends.
2.1.1. Reset Sequence
After power-on, the modem must be reset by asserting the RESET pin (low) for the required time then waiting a
fixed 300 ms before sending the first AT command. The reset recovery time of 300 ms is also applicable if the reset
is a SW triggered event, such as an ATZ command.
If a 4.9152 MHz crystal or an external 27 MHz clock is used, the reset must be asserted for 5 ms, and a wait of
300 ms duration must happen before an AT command is issued. If a 32 kHz crystal is used, the reset pulse must be
500 ms long and followed by the same 300 ms duration wait as that used for higher frequency clocks.
This is adequate to reset all the on-chip registers. Note that 16 µs after the customer-applied reset pulse starts, the
I/O pins will be tri-stated with a weak pull-up, and, 16 µs after the end of this reset pulse, the IO pins will switch to
inputs or outputs as appropriate to the mode indicated by the pull-down strapping. This 16 µs delay is for newer
revs of the modem parts (those parts that introduce a 32 kHz crystal and SPI operation); older revs exhibit a delay
of only nanoseconds.
The reset sequence described above is appropriate for all user modes of the modem including UART, SPI, and
Parallel bus operation.
A software reset of the modem can also be performed by issuing the command ATZ or by setting U-register 6E bit
4 (RST) high using AT commands. After issuing a software or hardware reset, the host must wait for the reset
recovery time before issuing any subsequent AT commands.
There is no non-volatile memory on the ISOmodem other than program ROM. When reset, the ISOmodem reverts
to the original factory default settings. Any set-up or configuration data and software updates must be reloaded
after every reset. This is true whether the reset occurs due to a power-down/power-up cycle, a power-on reset
through a manual reset switch, by writing U6E [4] (RST) = 1, or by executing ATZ.
A suggested reset sequence is as follows:
1. Apply an active-low pulse to the RESET pin; write RST bit or ATZ<CR>.
2. Wait at least the reset recovery time.
3. Load firmware updates (if required).
4. Set non-default DAA interface parameters—DCV, ACT, ILIM, OHS2, OHS, RZ, RT, (U67), LIM, (U68).
5. Set non-default cadence values—Busy Tone, Ringback, Ring.

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12 Rev. 1.3
6. Set non-default frequency values—Ring.
7. Set non-default filter parameters.
8. Set non-default S-register values.
The modem is now ready to detect rings, answer another modem, call, or dial out to a remote modem.
Some key default settings for the modem after reset or powerup include the following:
V.92 and fall-backs enabled (Si2494/93)
V.90 and fall-backs enabled (Si2457)
V.34 and fall-backs enabled (Si2439/34)
V.32bis and fall-backs enabled (Si2415)
V.22bis and fall-backs enabled (Si2404)
V.42/42bis enabled
+++ escape sequence enabled
Answer-on-ring is disabled
Speaker off
DTE echo enabled
Verbal result codes enabled
CTS only enabled
FCC (US) DAA and call progress settings
2.1.2. Reset Strapping: General Considerations
The different options available in the Si24xx ISOmodem family are selected by means of 10 kpulldown resistors
placed at certain pins. During power-on or pin reset, the ISOmodem’s signal pins are read and the option resistors
are taken into account to determine the required configuration. After reset, the ISOmodem assumes the
functionality selected by the corresponding combination of pulldown resistors.
Below is a summary of reset-strap options. Not all options are available on all part number or packages. Refer to
Table 4, “ISOmodem Capabilities,” on page 10 for details.
Host interface: UART, parallel or SPI
Input clock frequency: 32 kHz, 4.9152 MHz or 27 MHz
Autobaud mode or fixed-rate UART communication (when UART interface is selected). Disabling the autobaud
feature at reset sets the rate to 19,200 baud.
EEPROM interface
Three-wire EEPROM or four-wire EEPROM when EEPROM interface is selected
Refer to "2.6. EEPROM Interface (24-Pin TSSOP and 38-Pin QFN Only)" on page 31 for more details on the
various ISOmodem EEPROM options.
The next few sections describe the various reset options that must be selected for each package. In all the tables,
the following conventions apply:
0 means a 10 kpulldown resistor to ground.
1 means the pin is left open. If a pin is left open, the internal pullup resistor is normally sufficient as long as the
pin is not driven externally during reset. If there is noise or special power-sequencing situations, then an
external pullup resistor may be needed.

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Rev. 1.3 13
2.1.3. Reset-Strap Options for 16-Pin SOIC Package
The clock frequency and interface on the 16-pin SOIC package are selected according to Table 5 below. The
parallel interface, EEPROM and autobaud options are not available in the 16-pin SOIC package.
2.1.4. Reset-Strap Options for 24-Pin TSSOP Package
The pin-strapping options for the 24-pin TSSOP package are described in the three subsections below, depending
on the interface mode selected.
Table 5. SOIC-16 Reset-Strap Options
Mode Reset-Strap Pins
Interface Input Clock Pin 3
RI Pin 5, RXD/MISO Pin 7, CTS/SCLK Pin 11
INT Pin 15 DCD
UART 32 kHz 0 X 1 1 X
4.9152 MHz 1 X 1 1 1
27 MHz 1 X 1 1 0
SPI 32 kHz 1 1 X 0 1
4.9152 MHz 0 1 X 0 X
27 MHz 1 1 X 0 0

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14 Rev. 1.3
2.1.4.1. Reset Strapping Options for TSSOP-24 with UART-Interface
UART-interface options for the 24-pin TSSOP package are shown in Table 6 below.
2.1.4.2. Reset Strapping Options for TSSOP-24 with Parallel-Interface
Parallel-interface options for the 24-pin TSSOP package appear in Table 7 below. The EEPROM and autobaud
options are not available when the parallel interface is selected.
Table 6. TSSOP-24 UART-Interface Options
Mode Reset-Strap Pins
Input Clock Autobaud
Disabled? Three-Wire EEPROM
Interface?
Pin 4
FSYNC Pin 11, CTS
Pin 15, AOUT
Pin 16, INT
Pin 17
RI Pin 18 SDI/EESD Pin 23 DCD
32 kHz No No 1 1 0 1 X
Yes 0 1 0 1 X
Yes No 1 1 0 0 X
Yes 0 1 0 0 X
4.9152 MHz No No 1 1 1 1 1
Yes 0 1 1 1 1
Yes No 1 1 1 0 1
Yes 0 1 1 0 1
27 MHz No No 1 1 1 1 0
Yes 0 1 1 1 0
Yes No 1 1 1 0 0
Yes 0 1 1 0 0
Table 7. TSSOP-24 Parallel-Interface Options
Mode Reset-Strap Pins
Input Clock Pin 9, RD
Pin 10, WR Pin 11
SCLK Pin 15 INT
27 MHz 1 0 0
4.9152 MHz 1 1 0

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Rev. 1.3 15
2.1.4.3. Reset Strapping Options for TSSOP with SPI-Interface
Table 8 lists the SPI-interface options for the 24-pin TSSOP package.
2.1.5. Reset Strapping Options for QFN Parts
2.1.5.1. Reset Strapping Options for QFN Parts with UART Operation
Table 9 lists the reset strapping options for QFN parts with UART operation.
Table 8. TSSOP-24 SPI-Interface Clock-Frequency Options
Mode Reset-Strap Pins
Input Clock Three-Wire
EEPROM
Interface?
Pin 4
FSYNC Pin 9, RXD
Pin 11, SCLK
Pin 15, AOUT
Pin 18, SDI/EESD
Pin 16
INT Pin 17
RI Pin 23 DCD
32 kHz No 1 1 0 1 1
Yes 0 1 0 1 1
4.9152 MHz No 1 1 0 0 X
Yes 0 1 0 0 X
27 MHz No 1 1 0 1 0
Yes 0 1 0 1 0
Table 9. Reset Strapping Options for QFN Parts with UART Operation
Input Clk Auto-Baud
Disable Three-Wire EEPROM
Interface
FSYNCH CTS AOUT EECLK INT RI SDI DCD
Pin 2 Pin 21 Pin 15 Pin 13 Pin 35 Pin 19 Pin 8 Pin 28
32 kHz No No 1 1 1 1 1 1 1 1
Yes 0 1 1 1 1 1 1 1
Yes No 1 1 1 1 1 1 0 1
Yes 0 1 1 1 1 1 0 1
4.9152 MHz No No 1 1 1 1 1 0 1 X
Yes 0 1 1 1 1 0 1 X
Yes No 1 1 1 1 1 0 0 X
Yes 0 1 1 1 1 0 0 X
27 MHz No No 1 1 1 1 1 1 1 0
Yes 0 1 1 1 1 1 1 0
Yes No 1 1 1 1 1 1 0 0
Yes 0 1 1 1 1 1 0 0

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16 Rev. 1.3
2.1.5.2. Reset Strapping Options for QFN Parts with SPI Operation
Table 10 lists the reset strapping options for QFN parts with SPI operation.
2.1.5.3. Reset Strapping Options for QFN Parts with Parallel Operation
Table 11 lists the reset strapping options for QFN parts with parallel operation.
Table 10. Reset Strapping Options for QFN parts with SPI Operation
Input Clk Three-Wire
EEPROM
Interface
FSYNCH AOUT EECLK INT RI SDI DCD MISO
Pin 2 Pin 15 Pin 13 Pin 35 Pin 19 Pin 8 Pin 28 Pin 22
32 kHz No 1 1 1 0 1 1 1 1
Yes 0 1 1 0 1 1 1 1
4.9152 MHz No 1 1 1 0 0 1 X 1
Yes 0 1 1 0 0 1 X 1
27 MHz No 1 1 1 0 1 1 0 1
Yes 0 1 1 0 1 1 0 1
Table 11. Reset Strapping Options for QFN Parts with Parallel Operation
Input Clk CS AOUT EECLK RD
Pin 21 Pin 15 Pin 13 Pin 22
32 kHz 1 0 1 1
10 1 1
4.9152 MHz 1 0 0 1
10 0 1
27 MHz 0 0 1 1
00 1 1

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Rev. 1.3 17
2.2. System Interface
The ISOmodem can be connected to a host processor through a UART, SPI or parallel interface. Connection to the
chip requires low-voltage CMOS signal levels from the host and any other circuitry interfacing directly. The
following sections describe the digital interface options in detail.
2.2.1. Interface Selection
The interface is selected during reset, as described in "2.1. Resetting the Device". Tables 12, 13, and 14 show the
functions of the affected pins for possible interface modes for 16-, 24- and 38-pin packages, respectively.
Table 12. Pin Functions vs. Interface Mode (SOIC-16)
Pin # UART Mode SPI Mode
3RI RI
5 RXD MISO
6 TXD MOSI
7CTS SCLK
11 INT INT
14 ESC ESC
15 DCD DCD
16 RTS SS
Table 13. Pin Functions vs. Interface Mode (TSSOP-24)
Pin # UART Mode SPI Mode Parallel Mode
2 FSYNC (SSI) FSYNC (SSI) D6
3 CLKOUT (SSI) CLKOUT (SSI) A0
8RTS SS D7
9 RXD MISO RD
10 TXD MOSI WR
11 CTS SCLK CS
15 AOUT AOUT INT
16 INT INT D0
17 RI RI D1
18 SDI (SSI) SDI (SSI) D2
22 ESC ESC D3
23 DCD DCD D4
24 SDO (SSI) SDO (SSI) D5

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18 Rev. 1.3
Table 14. Pin Functions vs. Interface Mode (QFN-38)
Pin # UART Mode SPI Mode Parallel Mode
35 INT INT INT
34 GPIO18 GPIO18 D0
33 GPIO17 GPIO17 D1
32 GPIO16 GPIO16 D2
31 GPIO23 GPIO23 D3
30 GPIO24 GPIO24 D4
29 ESC D5
28 DCD D6
24 RTS SS D7
23 TXD MOSI WR
22 RXD MISO RD
21 CTS SCLK CS
20 GPIO11 GPIO11 A0
19 RI

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Rev. 1.3 19
2.2.2. Interface Signal Description
The following tables describe each set of UART, parallel and SPI interface signals:
2.2.3. UART Interface Operation
The UART interface allows the host processor to communicate with the modem controller through a UART driver.
In this mode, the modem is analogous to an external “box” modem. The interface pins are 5 V tolerant and
communicate with TTL-compatible, low-voltage CMOS levels. RS232 interface chips, such as those used on the
modem evaluation board, can be used to make the UART interface directly compatible with a PC or terminal serial
port.
2.2.3.1. UART Options
The DTE rate is set by the autobaud feature after reset. When autobaud is disabled, the UART is configured to
19.2 kbps, 8-bit data, no parity and 1 stop bit on reset. The UART data rate is programmable from 300 bps to
307.2 kbps with the AT\Tn command (see Table 42, “Extended AT\ Command Set,” on page 81). After the AT\Tn
command is issued, the ISOmodem echoes the result code at the old DTE rate. After the result code is sent, all
subsequent communication is at the new DTE rate.
The DTE baud clock is within the modem crystal tolerance (typically ±50 ppm), except for DTE rates that are
uneven multiples of the modem clock. All DTE rates are within the +1%/–2.5% required by the V.14 specification.
Table 18 shows the ideal DTE rate, the actual DTE rate, and the approximate error.
Table 15. UART-Interface Signals
Signal Direction Description
TXD Input Data input from host TXD pin
RXD Output Data output to host RXD pin
RTS Input Active-low request-to-send input for flow control
CTS Output Clear to send: Si2493 is ready to receive data on the TXD pin (active low)
Table 16. SPI-Interface Signals
Signal Direction Description
SCLK Input Serial data clock
MISO Output Serial data output
MOSI Input Serial data input
SS Input Chip select (active low)
INT Output Interrupt (active low)
Table 17. Parallel-Interface Signals
Signal Direction Description
A0 Input Register selection (address input)
CS Input Chip select (active low)
RD Input Read enable (active low)
WR Input Write enable (active low)
D[7:0] Bidirectional Parallel data bus
INT Output Interrupt (active low)

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20 Rev. 1.3
The UART interface synchronizes on the start bits of incoming characters and samples the data bit field and stop
bits. The interface is designed to accommodate character lengths of 8, 9, 10, and 11 bits giving data fields of 6, 7,
8, or 9 bits. Data width can be set to 6, 7, or 8 bits with the AT\Bn command. Parity can be set to odd, even, mark,
or space by the AT\Pn command in conjunction with AT\B2 or AT\B5. Other AT\Bn settings have no parity.
Figure 2. Asychronous UART Serial Interface Timing Diagram
2.2.3.2. Autobaud
When set in UART interface mode, the ISOmodem includes an automatic baud rate detection feature that allows
the host to start transmitting data at any standard DTE rate from 300 bps to 307.2 kbps. This feature is enabled by
default. When autobaud is enabled, it continually adjusts the baud rate, and the ISOmodem always echoes result
codes at the same baud rate as the most recently received character from the host. Autobaud can be turned off
using AT commands \T0 through \T15, and \T17. Host software should disable autobaud operation once the DTE
rate has been established. This prevents transients on TXD to cause inadvertent baud rate changes.
Autobaud is off when dialing, answering, and in data mode. When autobaud mode is off, the baud rate is set to the
most recently-active baud rate prior to entering one of these states. When autobaud mode is on, autoparity is
performed when either “at” or “AT” is detected. Autoparity detects the formats listed in Table 19.
Table 18. DTE Rates
Ideal DTE Rate (bps) Actual DTE Rate (bps) Approximate Error(%)
300 300
600 600
1200 1200
2400 2400
7200 7202 0.01
9600 9600
12000 12003 0.02
14400 14400
19200 19200
38400 38400
57600 57488 0.2
115200 115651 0.4
230400 228613 0.8
245760 245760
307200 307200
D1D0 D2 D3 D4 D5 D6 D7
START
BIT
MARK STOP
BIT
BIT TIMES
BIT SAMPLING
SPACE
D1D0 D2 D3 D4 D5 D6 D7
START
BIT
MARK STOP
BIT
BIT TIMES
BIT SAMPLING
SPACE D8