SeaLevel Route 56 User manual

Part # 5011
Sealevel Systems, Inc
155 Technology Place
P.O. Box 830
Liberty, SC 29657 USA
Phone: [phone]
FAX: [phone]
www.sealevel.com
Route 56
USER MANUAL
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Contents
INTRODUCTION ........................................................................ 1
OVERVIEW ...........................................................................................1
WHAT’S INCLUDED..............................................................................1
FACTORY DEFAULT SETTINGS..............................................................1
CARD SETUP............................................................................. 2
ADDRESS SELECTION............................................................................2
INTERFACE SELECTION.........................................................................3
IRQ Selection...............................................................................4
INSTALLATION.......................................................................... 5
TECHNICAL DESCRIPTION ....................................................... 6
FEATURES............................................................................................6
IUSC™...............................................................................................7
RAM...................................................................................................7
CONTROL / STATUS REGISTERS DEFINITION.........................................8
Description...................................................................................9
I/O SIGNAL DERIVATION ...................................................................10
25 PIN CONNECTOR SIGNAL LAYOUTS (DB-25 MALE)....................11
RS-232 Signals...........................................................................11
V.35 Signals................................................................................11
V.35 Signals (continued) ...........................................................12
RS-530 (RS-422).......................................................................12
RS-530A......................................................................................12
RS-485 or RS-485T...................................................................13
SPECIFICATIONS..................................................................... 14
ENVIRONMENTAL SPECIFICATIONS.....................................................14
POWER CONSUMPTION......................................................................14
MEAN TIME BETWEEN FAILURES (MTBF)........................................14
PHYSICAL DIMENSIONS......................................................................14
APPENDIX A -TROUBLESHOOTING....................................... 15
APPENDIX B -HOW TO GET ASSISTANCE............................. 16
APPENDIX C -ELECTRICAL INTERFACE................................ 17
RS-232.............................................................................................17
RS-422.............................................................................................17
RS-530 / 530A................................................................................18
V.35..................................................................................................18

APPENDIX D -SILK-SCREEN.................................................. 19
APPENDIX E -COMPLIANCE NOTICES................................... 20
FEDERAL COMMUNICATIONS COMMISSION STATEMENT...................20
EMC DIRECTIVE STATEMENT ...........................................................20
WARRANTY............................................................................ 21
Figures
FIGURE 1 -ADDRESS SELECTION TABLE..............................................................2
FIGURE 2 -DIP-SWITCH ILLUSTRATION.............................................................2
FIGURE 3 –HEADER E1 IRQ SELECTION............................................................4
© 1999f Sealevel Systems, Incorporated. All rights reserved.

Introduction
Sealevel Systems ROUTE 56 Page 1
Introduction
Overview
The ROUTE 56 adapter provides the PC with a single channel high-speed
multi-protocol serial interface suitable for the most popular communication
protocols. This sync/async card provides an ideal solution for high-speed
applications including LAN/WAN connectivity. Utilizing the Z16C32
(IUSC™) on chip DMA controller eliminates bus bandwidth constraints that
are placed on typical PC interface adapters, allowing data rates to reach 10M
bps in burst mode. By utilizing the Z16C32's 32 byte FIFO buffer coupled with
256K of on board memory, higher data rates are achieved without increasing
processor overhead.
What’s Included
The ROUTE 56 is shipped with the following items. If any of these items are
missing or damaged, contact the supplier.
•ROUTE 56 Adapter
•ROUTE 56 Developers Toolkit Software
•ROUTE 56 User manual
Factory Default Settings
The ROUTE 56 factory default settings are as follows:
Base Address IRQ Default Electrical Interface
300 5RS-530/422
To install the ROUTE 56 using factory default settings, refer to Installation on
page 5.
For your reference, record installed ROUTE 56 settings below:
Base Address IRQ Default Electrical Interface

Card Setup
Sealevel Systems ROUTE 56 Page 2
Card Setup
The ROUTE 56 contains several jumper straps for each port, which must be set
for proper operation.
Address Selection
The ROUTE 56 adapter occupies a total of eight consecutive I/O locations. A
DIP-switch is used to set the base address for these locations. Be careful when
selecting the base address as some selections conflict with existing PC ports.
The following table shows several examples that usually do not cause a
conflict.
Address Binary Switch Settings
Hex A9 A8 A0 123456
238-23F 1000111XXX On On On Off Off Off
300-307 1100000XXX Off On On On On On
308-30F 1100000XXX Off On On On On On
310-317 1100010XXX Off On On On Off On
318-31F 1100010XXX Off On On On Off On
320-327 1100100XXX Off On On Off On On
3A0-3A7 1110100XXX Off Off On Off On On
Figure 1-Address Selection Table
The following illustration shows the correlation between the DIP-switch
setting and the address bits used to determine the base address. Assume 300
Hex to 307 Hex is the desired base address. 300 Hex = (1) 1 0000 0X in
Binary.
1 2
3
4
5
6
ON
OFF
A8 A3
Figure 2-DIP-Switch Illustration
Note:Setting the switch “On” or “Closed” corresponds to a “0” in the address,
while leaving it “Off” or “Open” corresponds to a “1”.

Card Setup
Sealevel Systems ROUTE 56 Page 3
Interface Selection
The Route 56 supports a variety of electrical interfaces. These interfaces may
be selected in two ways. The determining bit is found at Base+5, bit position
D4, and is identified as IFSEL (InterFace SELect). Reference the
Control/Status Register Descriptions, found in the Technical Descriptionsection
of this manual for this bit description. When IFSEL = 0, then the values read
from M3-M0 are determined by the DIP-switch SW2. If all the switches on
SW2 are off, then all drivers and receivers are in a high impedance state. Only
one switch should be set to the on position at a time. The following example
illustrates SW-2:
1 2 3 4 5 6
ON
OFF
RS-232 RS-530
RS-530A
RS-485T
RS-485
V.35
When IFSEL = 1, then the values read from M3-M0 are determined by values
written to base+5 register. If this method is utilized, all switches on SW2
should be set in the off position, unless a default value is required. This
prevents the application of excess voltages on power-up to external receivers.
The following table shows the valid options.
HEX M3 M2 M1 M0 INTERFACE MODE
00000all signals are high impedance
10001* not supported *
20010RS-232
30011* not supported *
40100RS-485 with 120 ohm termination
50101RS-485 without termination
6,7,8,9 0110* not supported *
A1010single ended loop-back
B1011differential loop-back
C1100* not supported *
D1101RS-530
E1110V.35
F1111RS-530A

Card Setup
Sealevel Systems ROUTE 56 Page 4
IRQ Selection
Header E1 is used to select the interrupt request for each the Route 56. In the
example below, IRQ12 is selected. This setting must be made prior to installing
the adapter. Please query your system to determine the best available IRQ to
use.
3 4
5
7
10
11
12
15
9
Figure 3–Header E1 IRQ Selection

Installation
Sealevel Systems ROUTE 56 Page 5
Installation
The ROUTE 56 can be installed in any of the 16-bit ISA expansion slots. The
ROUTE 56 contains several jumper straps for each port, which must be set for
proper operation.
1. Turn off PC power. Disconnect the power cord.
2. Remove the PC case cover.
3. Locate an available slot and remove the blank metal slot cover.
4. Gently insert the ROUTE 56 into the slot. Make sure the adapter is seated
properly.
5. Replace the screw.
6. Replace the cover.
7. Connect the power cord.
Installation is complete.
The ROUTE 56 has a number of cabling options available. These options
include:
•CA-103 -This cable provides a high quality shielded cable with the V.35
mechanical specification met on one end and a DB-25S (female) on the
other end. V.35 has a mechanical specification that is impossible to place
on a PC bracket and requires this adapter cable.
•CA-104 -This cable provides a 6’ extension for use with RS-232, and
RS-530.
•CA-107 -RS-530 (DB-25P) to RS-449 (DB-37P) cabling adapter. RS-530
is replacing RS-449 in Telecom applications, but there is still a very large
base of installed equipment that uses the RS-449 pin-out. Both standards
use RS-422 to define the electrical specifications and are interchangeable
via this adapter cable.
Note: DSR is not available on the card as shipped but can be enabled by placing
a 0-ohm resistor at R30 and removing the 0-ohm resistor at R31. This
will disable the use of Ring Indicator on RS-232, V.35, and RS-530A.
Operation System Installation
Windows NT Users Only
Select Install Software at the beginning of the CD and follow the instructions
for installing the HDLC C32 driver located under Synchronous/Asynchronous
software installation selection.

Technical Description
Sealevel Systems ROUTE 56 Page 6
Technical Description
The Sealevel Systems ROUTE 56 adapter was designed for seamless
integration into any ISA based system. The ROUTE 56 adapter requires a
80286 or higher CPU, one IRQ, a 8 byte block of I/O address and a 16K block
of memory address. The memory range of this adapter is configured to reside
in the lower 1-Megabyte of memory and appears to the system as a bank
switched 16K window. The ROUTE 56 adapter's memory range can be disabled
allowing multiple adapters to share the same block of memory.
Features
•Single channel high speed sync/async wide area network (WAN)
interface
•RS-232, RS-422/449, EIA-530, V.35 and RS-485 serial interface
capability with versatile cabling options
•Multi-protocol capable including: PPP (point-to-point protocol),
Frame Relay, X.25, high-speed Async, Bi-Sync, Mono-Sync, HDLC,
SDLC
•Ideal for T1, Fractional T1, E1, and ISDN applications
•On-board Z16C32 (IUSC™) with built in DMA controller and 32 byte
FIFO buffer
•Up to 10 Mbps burst mode
•256K of on-board RAM
•Link list DMA supported
•16-bit data path
•Off loads communication processing
•OEM Security Feature available

Technical Description
Sealevel Systems ROUTE 56 Page 7
IUSC™
The ROUTE 56 adapter is based on a single Zilog Z16C32 IUSC (Integrated
Universal Serial Controller). Application and driver software access the IUSC
registers through the first 256 bytes of on-board RAM. Register access to the
IUSC can be disabled via I/O registers allowing the first 256 bytes of RAM to
be used for buffer storage. The IUSC has a built-in DMA controller that allows
high-speed data transfers directly to and from the 256K block of on-board
memory. The IUSCs built-in DMA controller supports 4 different modes of
DMA transfer: Single Buffer, Pipelined, Array, and Link List. An on-board
16MHz oscillator clocks the IUSC.
RAM
The ROUTE 56 has 256K of on-board SRAM. The 256K bytes of SRAM
appear to the host processor in the 2nd 512K bytes of the host’s memory
address range, (Segment 80000 to F0000). This 256K of SRAM is in a 16K
bank-switched window. The address of the 16K window and the page is
software selectable. The IUSC always views the 256K of SRAM as linear
memory. The SRAM can be selectively disabled through software. The SRAM
should be addressed in a section that does not conflict with system memory
(i.e. I/O adapters, Video Memory, BIOS/BIOS extensions.)
Low Address Mode
Selected
512K (80000)
1 MB (FFFFF)
16K Address Window
for Bank Switching
(D0000-D4000)

Technical Description
Sealevel Systems ROUTE 56 Page 8
Control / Status Registers Definition
The I/O register base address is selected by SW1. The address range is 200H to 3FFH. The control / status registers
occupies 8 consecutive locations. The following tables provide a functional description of the bit positions.
X = do not care { }= always this value
Address Mode D7 D6 D5 D4 D3 D2 D1 D0
Base+0 RD MEMEN IUSCEN {0} {0} P17 P16 P15 P14
Base+0 WR MEMEN IUSCEN XXP17 P16 P15 P14
Base+1 RD {0} {0} {0} MA18 MA17 MA16 MA15 MA14
Base+1 WR INT2 INT1 INT0 MA18 MA17 MA16 MA15 MA14
Base+2 RD {0} WSEN {1} {0} {0} {0} {0} {0}
Base+2 WR XWSEN XXXXXX
Base+3 RD {0} {0} INTPEND RESTAT {1} {0} {0} {0}
Base+3 WR Software board reset XXXXXXX
Base+4 RD SHARE IRQEN {0} {0} {0} {0} {0} {0}
Base+4 WR SHARE XXXXXXX
Base+5 RD LL RL {0} IFSEL M3 M2 M1 M0
Base+5 WR LL RL XIFSEL M3 M2 M1 M0
Base+6 RD SD7 SD6 SD5 SD4 SD3 SD2 SD1 SD0
Base+7 RD SD15 SD14 SD13 SD12 SD11 SD10 SD9 SD8

Technical Description
Sealevel Systems ROUTE 56 Page 9
Field Description
MEMEN 1 = Host access to RAM or IUSC enabled; 0 = Host access to RAM or IUSC disabled.
IUSCEN 1 = Enable Host access to RAM; 0 = Enable Host access to IUSC.
P17-P14 These bits select which of sixteen 16K ram pages is visible at the address selected by MA18-MA14.
MA18-14 These bits select the base memory address of the 16K bank-switched window of the 256K SRAM.
INT2-INT0 Interrupt: 000 = Interrupts disabled, Interrupts enabled for all other values 001-111.
IRQEN 1 = Interrupts enabled, 0 = Interrupts disabled (Status Bit, Read Only)
SHARE 1= IRQ sharing enabled ;0= IRQ sharing disabled. ( 0 on power up)
INTPEND IUSC interrupt status: 1 = No interrupt pending on IUSC; 0 = Interrupt pending on IUSC.
RESTAT Reset status: 1 = On-board reset inactive; 0 = On-board reset active.
WSEN Wait State Enable: 1 = disable wait states (Zero wait states); 0 = enable wait states. ( 0 on power up )
RL Remote loopback
LL Local loopback
IFSEL 0 = DIP-switch interface select, 1 = Base+5 register M3-M0 interface select. ( 0 on power up )
M0-M3 I/O mode select to SP505
If IFSEL = 0, the value read is equal to the switch setting
If IFSEL = 1, the value read is the value written
See table for valid interface options
SD0-SD15 Optional security feature. Unique value per customer or application. ( default value = FFFF)

Technical Description
Sealevel Systems ROUTE 56 Page 10
I/O Signal Derivation
The Route 56 input/output signals are directly generated via the Zilog 16C32
IUSC. The following table defines these signals, their origin pin and signal
name following the conventions set by the 16C32 user’s manual. If using a
Sealevel Systems, Inc. supplied driver, this is for informational use only.
Signal Source
Transmit Data 16C32 TXD Pin
Request To Send 16C32 Port7 Pin
Data Terminal Ready 16C32 Port6 Pin
Transmit Signal Element Timing 16C32 TXC Pin
Receive Data 16C32 RXC Pin
Clear To Send 16C32 CTS Pin
Data Set Ready 16C32 RXREQ Pin
Data Carrier Detect 16C32 DCD Pin
Transmit Clock 16C32 TXCO Pin
Receive Clock 16C32 RXCO Pin
Ring Indicator 16C32 TXREQ Pin

Technical Description
Sealevel Systems ROUTE 56 Page 11
25 Pin Connector Signal Layouts (DB-25 Male)
RS-232 Signals
Dip-Switch SW2-1 or Base+5, M3-M0=2, 0010
Signal Name Pin # Mode
GND Ground 7
RD Receive Data 3Input
CTS Clear To Send 5Input
DSR Data Set Ready 6 Input
DCD Data Carrier Detect 8 Input
TM Test Mode 25 Input
RI Ring Indicator 22 Input
TXC Transmit Clock 15 Input
RXC Receive Clock 17 Input
TSET Transmit Signal Element Timing 24 Output
DTR Data Terminal Ready 20 Output
TD Transmit Data 2Output
RTS Request To Send 4Output
LL Local Loop-back 18 Output
RL Remote Loop-back 21 Output
Technical Note: Please terminate any control signals that are not going to be
used. The most common way to do this is connect RTS to CTS and RI. Also,
connect DCD to DTR and DSR. Terminating these pins, if not used, will help
insure you get the best performance from your adapter.
V.35 Signals
DIP-Switch SW2-6 or Base+5, M3-M0=E, 1110
Signal Name DB-25 V.35 Mode
GND Ground 7B
RDB RX+ Receive Positive 16 T Input
RDA RX-Receive Negative 3RInput
TXCB TXC+ Transmit Clock Positive 12 AA Input
TXCA TXC-Transmit Clock Negative 15 YInput
RXCB RXC+ Receive Clock Positive 9XInput
RXCA RXC-Receive Clock Negative 17 VInput
TDB TX+ Transmit Positive 14 SOutput
TDA TX-Transmit Negative 2POutput
TSETB TSET+ Transmit Signal Element Timing + 11 WOutput
TSETA TSET-Transmit Signal Element Timing -24 UOutput
CTS Clear To Send 5DInput *
DSR Data Set Ready 6EInput *

Technical Description
Sealevel Systems ROUTE 56 Page 12
V.35 Signals (continued)
DCD Data Carrier Detect 8FInput *
RI Ring Indicator 22 JInput *
DTR Data Terminal Ready 20 HOutput *
RTS Request To Send 4COutput *
LL Local Loop-back 18 Output *
RL Remote Loop-back 21 Output.*
* Note:All modem control signals are single ended (un-balanced) with RS-232
signal levels.
RS-530 (RS-422)
DIP-Switch SW2-2 or Base+5, M3-M0=D, 1101
Signal Name Pin # Mode
GND Ground 7
RDB RX+ Receive Positive 16 Input
RDA RX-Receive Negative 3Input
CTSB CTS+ Clear To Send Positive 13 Input
CTSA CTS-Clear To Send Negative 5Input
DCDB DCD+ Data Carrier Detect Positive 10 Input
DCDA DCD-Data Carrier Detect Negative 8Input
TXCB TXC+ Transmit Clock Positive 12 Input
TXCA TXC-Transmit Clock Negative 15 Input
RXCB RXC+ Receive Clock Positive 9Input
RXCA RXC-Receive Clock Negative 17 Input
TDB TX+ Transmit Positive 14 Output
TDA TX-Transmit Negative 2Output
RTSB RTS+ Request To Send Positive 19 Output
RTSA RTS-Request To Send Negative 4Output
DTRB DTR+ Data Terminal Ready Positive 23 Output
DTRA DTR-Data Terminal Ready Negative 20 Output
TSETB TSET+ Transmit Signal Element Timing Positive 11 Output
TSETA TSET-Transmit Signal Element Timing Negative 24 Output
DSR is not available on the card as shipped but can be enabled by placing a
0-ohm resistor at R30 and removing the 0-ohm resistor at R31. This will
disable the use of Ring Indicator on RS-232, V.35, and RS-530A. In this mode
the following signals are supported.
DSRB DSR+ Data Set Ready Positive 22 Input
DSRA DSR-Data Set Ready Negative 6Input
RS-530A
DIP-Switch SW2-3 or Base+5, M3-M0=F, 1111

Technical Description
Sealevel Systems ROUTE 56 Page 13
Signal Name Pin # Mode
GND Ground 7
RDB RX+ Receive Positive 16 Input
RDA RX-Receive Negative 3Input
CTSA CTS-Clear To Send Negative 5Input
DCDA DCD-Data Carrier Detect Negative 8Input
RIA Ring Indicator Negative 22 Input
TXCB TXC+ Transmit Clock Positive 12 Input
TXCA TXC-Transmit Clock Negative 15 Input
RXCB RXC+ Receive Clock Positive 9Input
RXCA RXC-Receive Clock Negative 17 Input
TDB TX+ Transmit Positive 14 Output
TDA TX-Transmit Negative 2Output
RTSA RTS-Request To Send Negative 4Output
DTRA DTR-Data Terminal Ready Negative 20 Output
TSETB TSET+ Transmit Signal Element Timing Positive 11 Output
TSETA TSET-Transmit Signal Element Timing Negative 24 Output
LL Local Loop-back 18 Output
RL Remote Loop-back 21 Output
RS-485 or RS-485T
RS-485T DIP-Switch SW2-4 or Base+5, M3-M0=4, 0100
RS-485T DIP-Switch SW2-5 or Base+5, M3-M0=4, 0101
Signal Name Pin # Mode
GND Ground 7
RDB RX+ Receive Positive 16 Input
RDA RX-Receive Negative 3Input
TXCB TXC+ Transmit Clock Positive 12 Input
TXCA TXC-Transmit Clock Negative 15 Input
RXCB RXC+ Receive Clock Positive 9Input
RXCA RXC-Receive Clock Negative 17 Input
TDB TX+ Transmit Positive 14 Output
TDA TX-Transmit Negative 2Output
TSETB TSET+ Transmit Signal Element Timing Positive 11 Output
TSETA TSET-Transmit Signal Element Timing Negative 24 Output
LL Local Loop-back 18 Output
RL Remote Loop-back 21 Output

Specifications
Sealevel Systems ROUTE 56 Page 14
Specifications
Environmental Specifications
Specification Operating Storage
Temperature Range 0 to 50 º C
(32 to 122 º F) -20 to 70 º C (-4 to 158 ºF)
Humidity Range 10 -90% R.H.
NonCondensing 10 -90% R.H. NonCondensing
Power Consumption
Supply line +5 VDC
Rating 500mA
Mean Time Between Failures (MTBF)
Greater than 150,000 hours. (Calculated)
Physical Dimensions
Board length 6.095 inches (15.4813 cm.)
Board Height including Goldfingers 3.40 inches (8.636 cm.)
Board Height excluding Goldfingers 3.10 inches (7.874 cm.)

Appendix A -Troubleshooting
Sealevel Systems ROUTE 56 Page 15
Appendix A -Troubleshooting
The Developers Toolkit Software is supplied with the Sealevel Systems adapter
and will be used in the troubleshooting procedures. Using this software and
following these simple steps can eliminate most common problems without the
need to call Technical Support.
1. Identify all I/O adapters currently installed in your system. This includes
your on-board serial ports, controller cards, sound cards etc. The I/O
addresses used by these adapters, as well as the IRQ (if any) should be
identified.
2. Configure your Sealevel Systems adapter so that there is no conflict with
currently installed adapters. No two adapters can occupy the same I/O
address.
3. Make sure the Sealevel Systems adapter is using a unique IRQ. While the
Sealevel Systems adapter does allow the sharing of IRQs, many other
adapters (i.e. SCSI adapters and on-board serial ports) do not. The IRQ is
typically selected via an on-board header block. Refer to the section on
Card Setup and the Control/Status port for help in choosing an I/O address
and IRQ.
4. Make sure the Sealevel Systems adapter is securely installed in a 16-bit
slot.
5. Use the supplied software and User Manual to verify that the Sealevel
Systems adapter is configured correctly. The supplied software contains a
diagnostic program “SSDR56” that will verify if an adapter is configured
properly. This diagnostic program is written with the user in mind and is
easy to use. Refer to the “README.txt” file on the supplied software for
detailed instructions on using “SSDR56”.
6. The following are known I/O conflicts:
•The 278 and 378 settings may conflict with your printer I/O
adapter.
•3B0 cannot be used if a Monochrome adapter is installed.
•3F8-3FF is typically reserved for COM1:
•2F8-2FF is typically reserved for COM2:
•3E8-3EF is typically reserved for COM3:
•2E8-2EF is typically reserved for COM4:

Appendix B -How To Get Assistance
Sealevel Systems ROUTE 56 Page 16
Appendix B -How To Get Assistance
Please refer to Appendix A -Troubleshooting prior to calling Technical
Support.
1. Read this manual thoroughly before attempting to install the
adapter in your system.
2. When calling for technical assistance, please have your user
manual and current adapter settings. If possible, please have the
adapter installed in a computer ready to run diagnostics.
3. Sealevel Systems maintains a Home page on the Internet. Our
home page address is www.sealevel.com. The latest software
updates, and newest manuals are available via our FTP site that can
be accessed from our home page.
4. Technical support is available Monday to Friday from 8:00 a.m. to
5:00 p.m. eastern time. Technical support can be reached at (864)
843-4343.
RETURN AUTHORIZATION MUST BE OBTAINED FROM SEALEVEL
SYSTEMS BEFORE RETURNED MERCHANDISE WILL BE ACCEPTED.
AUTHORIZATION CAN BE OBTAINED BY CALLING SEALEVEL
SYSTEMS AND REQUESTING A RETURN MERCHANDISE
AUTHORIZATION (RMA) NUMBER.

Appendix C -Electrical Interface
Sealevel Systems ROUTE 56 Page 17
Appendix C -Electrical Interface
RS-232
Quite possibly the most widely used communication standard is RS-232. This
implementation has been defined and revised several times and is often
referred to as RS-232 or EIA/TIA-232. It is defined by the EIA as the Interface
between Data Terminal Equipment and Data Circuit-Terminating
Equipment Employing Serial Binary Data Interchange. The mechanical
implementation of RS-232 is on a 25 pin D sub connector. RS-232 is capable
of operating at data rates up to 20 Kbps at distances less than 50 ft. The
absolute maximum data rate may vary due to line conditions and cable lengths.
RS-232 often operates at 38.4 Kbps over very short distances. The voltage
levels defined by RS-232 range from -12 to +12 volts. RS-232 is a single
ended or unbalanced interface, meaning that a single electrical signal is
compared to a common signal (ground) to determine binary logic states. A
voltage of +12 volts (usually +3 to +10 volts) represents a binary 0 (space) and
-12 volts (-3to -10 volts) denotes a binary 1 (mark). The RS-232 and the
EIA/TIA-574 specification defines two type of interface circuits, Data
Terminal Equipment (DTE) and Data Circuit-Terminating Equipment (DCE).
The Sealevel Systems adapter is a DTE interface.
RS-422
The RS-422 specification defines the electrical characteristics of balanced
voltage digital interface circuits. RS-422 is a differential interface that defines
voltage levels and driver/receiver electrical specifications. On a differential
interface, logic levels are defined by the difference in voltage between a pair of
outputs or inputs. In contrast, a single ended interface, for example RS-232,
defines the logic levels as the difference in voltage between a single signal and
a common ground connection. Differential interfaces are typically more
immune to noise or voltage spikes that may occur on the communication lines.
Differential interfaces also have greater drive capabilities that allow for longer
cable lengths. RS-422 is rated up to 10 Megabits per second and can have
cabling 4000 feet long. RS-422 also defines driver and receiver electrical
characteristics that will allow 1 driver and up to 32 receivers on the line at
once. RS-422 signal levels range from 0 to +5 volts. RS-422 does not define a
physical connector.