Cermetek XE2422H User manual

Low-Cost, Low-Speed Surface-Mount Modem
©2009 Cermetek Microelectronics, Inc. Page 1 Document No. 607-0044 Revision A (12/11)
DESCRIPTION
The Cermetek XE2422H is a complete 2400 bps
modem in a miniature surface-mount module. It
permits the designer to easily incorporate dial-up
communications into set top box, security,
vending, or point-of-sale applications.
The XE2422H is a complete modem not just a
modem chip. Connections to the micro-controller
serial port and to the telephone line are all that is
required to design-in the XE2422H. As a
complete modem, Cermetek includes transferable
FCC Part 68 Registration. Eliminating the need
for Cermetek customers to under go FCC Part 68
testing.
The XE2422H provides the lowest total cost of
ownership. As a complete modem, it eliminates
modem design and certification costs. It reduces
assembly costs by replacing multiple components
with a single, surface-mount module. And all of
this is provide at a low per unit cost of less than
twenty dollars in volume.
FEATURES
 Small Size: 1.60” by 0.80” by 0.152”
 Data transfer rates from 300 bps to 2400 bps
• Supports V.21, V.22, V.22bis, V.23, Bell 103,
Bell 212A modem protocols
• Supports Pulse and FSK Alarm formats
 Serial data rates to 115,200 bps.
 Control and configuration via AT Commands
 3.3 and 5 volt compatible Serial Interface
 Shared Line Features prevent interference with
voice communications on an extension
telephone.
 Complete integrated DAA.
 User Transferrable FCC Part 68 Registration
 UL60950 Recognition
 Low Operating Power, 3.3 Volts, 50 mW;
 Sleep Mode with Wake-on-Ring feature
 Power Down reduces current draw to 100 A
XE2422H BLOCK DIAGRAM

Cermetek Microelectronics, Inc XE2422H Surface Mount Modem Module
©2009 Cermetek Microelectronics, Inc. Page 2 Document No. 607-0028 Revision C (10/09)
XE2422H Mechanical Specifications
E
F
FF I
A
J
HG C
D
B
INCHES MILLIMETERS
DIMENSIONS MIN TYP MAX MIN TYP MAX
A 1.595 1.600 1.605 40.51 10.64 40.77
B 0.795 0.800 0.805 20.19 20.32 20.45
C 0.147 0.152 0.157 3.73 3.86 3.99
D 0.095 0.100 0.105 2.41 2.54 2.67
E 0.055 0.060 0.065 1.40 1.52 1.65
F 0.095 0.100 0.105 2.41 2.54 2.67
G 1.045 1.050 1.055 26.54 26.67 26.80
H 0.495 0.500 0.505 12.57 12.70 12.83
I 0.995 1.000 1.005 25.27 25.40 25.53
J 0.395 0.400 0.405 10.03 10.16 10.29

Cermetek Microelectronics, Inc XE2422H Surface Mount Modem Module
©2009 Cermetek Microelectronics, Inc. Page 3 Document No. 607-0028 Revision C (10/09)
XE2422H Pin Configuration
Top View
1
2
3
4
5
6
7
13
12
11
10
9
8
Tip
Ring
/DCD
/DTR
/RI
Reserved
GND
VCC
/INT
/CTS
/RESET
RXD
TXD
Pin Descriptions
PIN NAME DESCRIPTION
1 TIP The Ring and Tip signals connect the modem to the telephone line. FCC Part 68
Rules require a 1500 volt isolation barrier between the telephone line and all other
circuits. This isolation must be preserved throughout the system.
The telephone company places a DC “Battery” voltage across Tip and Ring on public
switched telephone lines. The XE2422H operates regardless of the polarity of this
voltage. The “Battery” voltage drives up to 120 milliampere of DC loop current.
UL60950 requires minimum creepage and clearances distances between the Tip and
Ring traces and all other circuits. Clearance is the shortest distance between
conductive circuits; creepage is the distance between conductive points along the
surface
2 RING The Ring and Tip signals connect the modem to the telephone line. FCC Part 68
Rules require a 1500 volt isolation barrier between the telephone line and all other
circuits. This isolation must be preserved throughout the system.
The telephone company places a DC “Battery” voltage across Tip and Ring on public
switched telephone lines. The XE2422H operates regardless of the polarity of this
voltage. The “Battery” voltage drives up to 120 milliampere of DC loop current.
UL60950 requires minimum creepage and clearances distances between the Tip and
Ring traces and all other circuits. Clearance is the shortest distance between
conductive circuits; creepage is the distance between conductive points along the
surface.
3 /DCD /DCD is an active low output from the modem that indicates the presence of a valid
carrier signal. The SE2 register controls /DCD in the XE2422H. The default state is for
/DCD to be disabled ATSE2=04 enables /DCD.

Cermetek Microelectronics, Inc XE2422H Surface Mount Modem Module
©2009 Cermetek Microelectronics, Inc. Page 4 Document No. 607-0028 Revision C (10/09)
PIN NAME DESCRIPTION
4 /DTR /DTR is an active low input to the modem. The operation of /DTR is controlled by
register SE2 and is normally disabled. When enabled, the modem will exit data mode
and enter command mode if /DTR is removed while the modem is on-line. In Pulse
and FSK Alarm modes raising /DTR is the only was to disconnect the data link.
5 /RI The /RI signal reports on the presence of an incoming ring signal. When a ring
occurs across Tip and Ring, the /RI output goes low and toggles with the cadence of
the ring signal. /RI is controlled by register S0D bit 6. The default condition is for /RI to
be disabled.
6 RESERVED Reserved for future use
7 GROUND Ground provides the reference voltage for all host interface signals.
8 TXD TXD provides the path for transmitted data and modem commands to be passed from
the host controller to the modem. A logic high on TXD represents a “Mark” condition
and a logic low represents a “Space” condition.
9 RXD RXD provides the path for received data and modem responses to be sent from the
modem to the host controller. A logic high on RXD represents a “Mark” condition and
a logic low represents a “Space” condition.
10 /RESET /RESET is an active low input which initiates a modem hardware reset.
11 /CTS /CTS is an active low output from the modem. The modem asserts /CTS to indicate
that it can accept data from the terminal equipment on TXD.
12 /INT /INT provides an active low hardware interrupt signal from the XE2422H. The
operation of this interrupt pin is programmable using registers SE2 and S08. /INT can
be programmed to indicate Loss of Carrier, Wake-on-Ring, Loss of Loop Current, or
Shared Line Activity. Once triggered the /INT line remains active until cleared by the
AT:I command.
13 VCC VCC provides 3.3 volt power to the modem.

Cermetek Microelectronics, Inc XE2422H Surface Mount Modem Module
©2009 Cermetek Microelectronics, Inc. Page 5 Document No. 607-0028 Revision C (10/09)
XE2422H Electrical Specifications
PARAMETER MIN TYP MAX UNITS COMMENTS
VCC 3.0 3.3 3.6 VOLTS
15 mA On-Line
10 mA Sleep
ICC
1 mA Power Down
RING VOLTAGE DETECT 26 150 VRMS Type B Ringer
RING FREQUENCE DETECTED 15.3 68 Hz Type B Ringer
TELEPHONE LOOP CURRENT 16 40 120 mA
LINE IMPEDENCE 600 Ohms
DATA TRANSMIT LEVEL -9.0 dBm
DTMF TRANMIST LEVEL -2.5 0 dBm Average over a 3 second interval
Voh 2.4 Volts
Vol 0.4 Volts
Vih 2.0 5.0 Volts
ViL -0.3 0.8 VCC

Cermetek Microelectronics, Inc XE2422H Surface Mount Modem Module
©2009 Cermetek Microelectronics, Inc. Page 6 Document No. 607-0028 Revision C (10/09)
XE2422H Surface-Mount Soldering Instructions
The XE2422H is subject to damage if overexposed to heat during solder reflow operations. Following the
soldering instructions below will ensure that the process of soldering the module to the board does not
damage the modem.
Maximum Temperature 235OC
Maximum Time at 235OC 15 Seconds
Maximum Time above Eutectic (150OC) 90 Seconds
Maximum Preheat Dwell Time 180 Seconds
Maximum Recommended Solder Temperature Profile

Cermetek Microelectronics, Inc XE2422H Surface Mount Modem Module
©2009 Cermetek Microelectronics, Inc. Page 7 Document No. 607-0028 Revision C (10/09)
XE2422H Recommended Landing Pattern
Pad Dimensions: Oval 0.130 inches by 0.070 inches
Pad Extensions beyond XE2422H PCB: 0.040 inches
Row Center to Center: 0.74 inches
Warning: No Vias, Traces or other Copper should be placed under the XE2422H module

Cermetek Microelectronics, Inc XE2422H Surface Mount Modem Module
©2009 Cermetek Microelectronics, Inc. Page 8 Document No. 607-0028 Revision C (10/09)
XE2422H Typical Connection Diagram
VCC
/DCD
/CTS
RXD
TXD
/RI
/Reset
/INT
GND
RING
TIP (22)
RJ11
C1 C2
VCC
F1
To SystemReset
To Host SerialPort
To System Interrupt
XE2422H
Parts List for XE2422H Typical Connection Diagram
Reference
Designation Qty Description
C1, C2 2 Cap, 1000 pFd, 1500 V minimum
F1 1 PTC, TR600-150
Notes:
1 Capacitors, C1 and C2, may be required for EMI filtering in your system. Without these components
you may experience unintended radiation when the telephone cable is attached. C1 and C2 are high-
voltage capacitors. We recommend the Johanson Dielectrics 502S47N102KV6T. This 1000 pfd, 3000
volt capacitor will direct the high frequency harmonics to the system ground. These capacitors must be
rated at a minimum of 1500 volts to maintain the isolation required by FCC Part 68 Rules.
3. F1 is a positive thermal coefficient (PTC) device which protects the modem from excessive current flow.
These devices are required for your system to pass UL60950. Fuses may be used in place of the
PTC’s

Cermetek Microelectronics, Inc XE2422H Surface Mount Modem Module
©2009 Cermetek Microelectronics, Inc. Page 9 Document No. 607-0028 Revision C (10/09)
XE2422H DESIGN NOTES
The following design notes are intended to assist the developer in achieving maximum utility from the XE2422H
modem module.
XE2422H Shared Line Features
The XE2422H includes the ability to monitor telephone line conditions before, after and during calls. This
allows the XE2422H to avoid conflicts with other equipment connected to the telephone line. There are two
modes of operation for the XE2422H Shared Line Features; Connect Detect and Handset Interrupt.
Connect Detect
The XE2422H register SDB monitors the voltage level on the telephone line when the modem is on-hook.
The XE2422H checks the value of register SDB before attempting to go off-hook to avoid interrupting a call
in progress. The nominal value for loop voltage on the telephone line is typically 48 volts. A reduced
voltage level indicates that the line is either disconnected from the modem or is currently in use.
Register SDB is an 8 bit register. It stores the loop voltage as a 2’s complement number with each bit
representing 1 volt. The Most Significant Bit represents the polarity of the loop voltage.
Handset Interrupt:
Handset Interrupt permits the modem to yield the telephone line when other equipment connected to the
telephone line goes off-hook. This prevents the modem from blocking outgoing emergency calls when the
line is shared as in a residential application. Handset Interrupt is accomplished by monitoring the loop
current through the modem while the modem is off-hook. The loop current will drop when another piece of
equipment goes off-hook on the same telephone line.
The XE2422H constantly monitors and stores the loop current value in Register SF3 in 1.1 milliamp
increments. The value of SF3 is regularly updated. The value of SF3 is compared to the Handset Interrupt
threshold in register S12. If the value of SF3 is lower than the value of S12 by at least the amount of the
Handset Interrupt Differential Current Threshold, S11, then the XE2422H assumes the equipment on an
extension telephone has gone off-hook. The modem then issues the Handset Interrupt response “i” and if
so configured issues an Interrupt to the systems host controller. The host controller determines if the call
should be terminated to yield the telephone line to the extension.
XE2422H AT Commands
The XE2422H uses a simplified "AT" command set for configuration and control. This section describes
the AT command format and lists the AT commands, registers and result codes. XE2422H "AT" commands
have three operational modes; command mode, alarm mode and data mode. The Data Rate for the
XE2422H is set by Register SE0.
Data Mode: The XE2422H enters data mode after it connects to a remote modem and issues the
appropriate result code. In the data mode the modem sends all data presented on Transmit Data (TXD) to
the remote modem and puts data from the remote modem onto Received Data (RXD). When the modem
exits data mode, it issues a "NO CARRIER" result code.
Command Mode: The XE2422H enters command mode on power-up, reset, a lost connection, or receipt
of the escape code. In command mode the modem accepts commands from the host on transmit data.
Appropriate result codes are returned on RXD.

Cermetek Microelectronics, Inc XE2422H Surface Mount Modem Module
©2009 Cermetek Microelectronics, Inc. Page 10 Document No. 607-0028 Revision C (10/09)
Command Line Format
Command lines issued to the modem follow a strict format. Each command line begins with the prefix AT.
All commands except the “z” command must be entered in upper case characters. The command line is a
string of commands between the AT prefix and the carriage return which terminates the command. The
command buffer stores the command line and executes it upon receipt of a carriage return. Commands
will be executed in the sequence they appear in the command line.
Result Codes - The modem issues a result code after each command line. Result codes may be sent as
single characters or single characters followed by a carriage return.
Alarm Mode:
The XE2422H supports a unique set of commands to establish alarm industry connections. Both Pulse
messaging and FSK formats are supported. The AT!1 command initiates Pulse messaging and AT!2
initiates FSK messaging. The ATD command must precede either AT! command to begin the Alarm
transaction. In Alarm mode, /DTR must be removed to disconnect the modem link. /DTR is activated by
setting register SE2 bits 4 and 5.
Pulse Mode: In Pulse Mode messages are passed using DTMF tones. The receiving station
acknowledges receipt of the message by transmitting the “Kissoff” tone. A sample transaction is shown
below.
Alarm Panel XE2422H
ATDT#!1<message 1><CR>
K
!<message 2><CR>
K
!<message n><CR>
K
Disconnect is accomplished by raising /DTR.
FSK Mode: In FSK Mode messages are passed on a 300 bps, half-duplex carrier signal. The X1, X2, and
X3 commands switch the modem between monitoring the line for acknowledgments (X1), transmitting
messages (X2), and receiving messages (X3). As in the pulse mode disconnect is only possible by pulling
the /DTR signal high.