Brainboxes CC-310, PCI Velocity RS422, PCI Velocity RS485, PCI Opto RS422, PCI Opto RS485 Hardware Manual

Hardware Manual

1.12 EDITION MARCH 1998

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Guarantee.

FULL 36 MONTHS GUARANTEE.

We guarantee your Serial Port Card for a full 36 months from
purchase, parts and labour, provided it has been used in the
specified manner. In the unlikely event of failure return your
interface to your Dealer, with proof of purchase, who will
determine whether to repair or replace this product with an
equivalent unit.

COPYRIGHT.

COPYRIGHT © 1985-1998.

All rights reserved. No part of this hardware, circuitry or manual
may be duplicated, copied, transmitted or reproduced in any way
without the prior written consent of the Manufacturer.

Due to the Manufacturers commitment to quality, software is
subject to continuous improvements: information regarding
upgrades can be obtained from your supplier.

Serial Solutions is supplied to you by

ACKNOWLEDGEMENTS.

IBM, COMPAQ, Hewlett Packard, H.P. and EPSON are
trademarks of the relevant companies. Windows is a trademark of
Microsoft.

PCI VELOCITY / OPTO ISO RS422/485 Introduction

PCI OPTO ISOLATED RS422/485 AUTOGATING
PCI VELOCITY RS422/485 AUTOGATING

These products conform to the following standards :

CE standard: EN55022:1987 Class B

IEC 801-2: 1991 Level 2
IEC 801-3: 1984 Level 2
IEC 801-4: 1998 Level 2

PCB: IEC 249-2-5

NEMA L1 1-10
DIN 40802
UTE C 93-711
BS 4584
MIL P-13949E
UL Approved to 94 V0

TIA /EIA: 485 A (1995) ,423 B (1996)

Year 2000: DISC PD2000-1

Intro 1

Introduction PCI VELOCITY / OPTO ISO RS422/485

PCI VELOCITY RS422/485 AUTOGATING
PCI OPTO ISOLATED RS422/485 AUTOGATING

OUTLINE CONTENTS

Chapter 1 - Supplied Serial Solution Software.
Chapter 2 - PCI Velocity RS422/485 Specif icati ons.
Chapter 3 - PCI Dual RS422/485 Software

Configuration G uide.

Chapter 4 - Additional RS422/RS485 Information.

The Layout Of This Manual

Chapter 1 - Serial Solution Software, is an overview of

this companion software package for our range of serial portcards.

Chapter 2 - PCI Velocity RS422/485 Specifications,

gives details of the PCI Velocity RS422/485 specifications, details
of how to install the optional parallel port and shows you how to
install your PCI Velocity RS422/485 card.

Chapter 3 - PCI Velocity RS422/485 Software
Configuration Guide

operating system to successfully allow trouble free operation of
your PCI Velocity RS422/485 card. Installation procedures are for
DOS, Windows 3.x, Windows 95 / 98 and Windows NT.

, shows you how to configure your

Chapter 4 - Additional RS422/RS485 Information,

gives details on the RS422 and R485 standard, and cabling; as well
as examining half and full duplex RS485 systems and information
on card grounding systems.

Intro 2

PCI VELOCITY / OPTO ISO RS422/485 Introduction

Table of Contents

CHAPTER 1..................................................................................1

INTRODUCTION. ........................................................................1

Introducing Serial Solution Software....................................1

Serial Solutions For DOS.....................................................1

Serial Solutions For Windows 3.x.........................................3

Serial Solutions For Windows 95..........................................4

Serial Solutions For Windows NT........................................4

Complete Documentation and Technical Backup.................. 4

CHAPTER 2..................................................................................6

INTRODUCTION. ........................................................................6

General PCI RS422/485 Card Features................................. 6

General PCI RS422/485 Serial Port Features (cont)..............7

Autogating............................................................................7

Optical Isolation...................................................................8

Configuring The PCI RS422/485 Cards.............................11

RS485 Multiplex Jumper Settings.......................................11

Hardware Installation. ........................................................13

Problems!...........................................................................14

CHAPTER 3................................................................................15

INTRODUCTION. ......................................................................15

INSTALLING PORTS IN MICROSOFT WINDOWS 95 & 98.............15

PCI Velocity RS422/485 Card Settings In Windows 95 & 98.

...........................................................................................18

PCI RS422/485 Port Settings In Windows 95 & 98. .......... 19

CONFIGURING PORTS IN MICROSOFT WINDOWS NT 4.0........... 23

Software Installation...........................................................23

Examining Card Configuration...........................................24

Configuring Ports............................................................... 25

Intro 3

Introduction PCI VELOCITY / OPTO ISO RS422/485

Advanced Port Settings. ..................................................... 26

Uninstalling Serial Solutions PCI. ......................................28

CONFIGURING PORTS IN WINDOWS 3.X....................................29

Determining PCI RS422/485 Resources. ............................ 29

Windows 3.x Software Installation..................................... 30

Serial Port Installation........................................................31

Configuring The COM Ports. ............................................. 33

Deleting Ports in Windows................................................. 34

Restarting Windows...........................................................34

CONFIGURING PORTS IN DOS..................................................35

Determining PCI RS422/485 Resources. ............................ 35

NEWCOM.SYS Parameters...............................................36

Configuring And Installing NEWCOM.SYS ...................... 38

Modifying Command Line Parameters...............................39

CHAPTER 4................................................................................40

THE RS422 STANDARD........................................................... 40

THE RS485 STANDARD........................................................... 40

Terminat i n g Im p e d ance’s...................................................4 1

Fail Safe Open Circuit Detection........................................42

Fail Safe Short Circuit Protection.......................................42

RS422 OPERATION. ................................................................ 42

RS422 Serial Port Cables....................................................43

RS485 OPERATION. ................................................................ 44

RS485 Cable. ..................................................................... 45

RS485 One Talker - Many Listeners, Half Duplex.............. 45

RS485 Many Talkers- Many Listeners, Half Duplex...........46

RS485 Many Talkers- Many Listeners, Full Duplex...........47

OPTIONAL GROUNDING ARRANGEMENTS.................................49

INDEX ........................................................................................52

Intro 4

PCI VELOCITY / OPTO ISO RS422/485 Serial Solutions

Chapter 1

SERIAL

SOLUTIONS

SOFTWARE.

Introduction.

This chapter is a brief description of the Serial Solutions
software package; this can also be purchased SEPARATELY and
is available from YOUR DEALER.

Introducing Serial Solution Software.

The perfect partner for any Serial Port is Serial Solutions
Software! Serial Solutions is a fully featured suite of programs
designed to squeeze the most fr o m PC seri al com muni cat ions.

Serial Solutions is made up of the following components: -

Serial Solutions for DOS
Serial Solutions for Windows 3.x
Serial Solutions for Windows 95

Serial Solutions for Windows NT

All the Serial Soluti ons drive rs have the fol lowing fe atures: -

• Drivers for PC FIFO UARTs e.g. 16550 as well as the new

improved 32 byte 16650 and 64 byte 16750 UARTs.

• Support for any mix of RS232, RS422, and RS485 handshake

schemes.

• Support for wider range of Baud rates and for more than 4 serial

ports.

Serial Solutions For DOS.

Serial Solutions for DOS consists of the following

Chapter 1 Page 1

Serial Solutions PCI VELOCITY / OPTO ISO RS422/485

programs: ­NewCOM.sys A device driver, it supports COM1 to COM16,

allowing 16 serial ports to be used under DOS.
It also includes an interrupt handler for
enhanced performance with user definable
buffer sizes. Accessible from all DOS
languages, it is the heart of the Serial Solution.
It has extensive handshaking support,
implementing both hardware handshaking
using any combination of the DTR, DSR, CTS,
RTS, and DCD lines, and a software handshake

using the XON/XOFF protocol.
NewCOM24.sys A device driver providing support for 24 ports.
NewCOM32.sys A device driver providing support for 32 ports.
NewMode.exe A replacement for the DOS ’mode com...’

command. NewMode is used to set the serial

parameters, including the port address, IRQ line

used, the baud rate, parity and data and stop bit

options. Baud rates supported are from 110

baud to 115,200 baud! Included is a very handy

query mode that reports the settings of the

various serial ports. Flexible and fast!
EASY programs. The EASY disk contains short, simple to

understand and use EASYBAS, EASYC and

ASYPAS programs, providing straight forward,

file type I/O to serial ports with debug

information. Use these FIRST, base your

sample applications on them. Source code,

make files and compiled ready to run programs

supplied.
TERM programs A suite of larger terminal emulation programs

written in C (Cterm), Assembly language

(Aterm), Pascal (Pasterm), BASIC (BASterm)

and FORTRAN (FORterm ) show how to access

the NEWBIOS routines as well as the simple

Chapter 1 Page 2

PCI VELOCITY / OPTO ISO RS422/485 Serial Solutions

file I/O to ports. They contain many lines of

code and are thus harder to grasp. They

demonstrate in depth serial port programming

in a variety of languages but they are also

useful tools for using serial devices.
Comtest.exe Comtest is a short but invaluable program that is

used to check that the serial port at a particular I/O

address is functi oning correctly and is connected to

the particular IRQ line. The program correctly

identifies the UART type b y employing the bu ilt in

loop back capability of the PC serial port chip, a

full test of the bau d rate genera to r, trans mittin g and

receiving buffer, parity enable and start stop bit is

performed. There is no need for a second serial

port or a cable when using this utility.

Serial Solutions For Windows 3.x

Serial Solutions for Windows 3.x works with Windows 3.0,

3.1 and 3.11 as well as Windows For Workgroups 3.11.

Serial Solutions for Windows 3.x consists of the following
programs: ­Setup.exe The install routine for the package.
Port.DLL Enhanced Control Panel applet. Allows

configuration of extra serial ports from the
Windows Control Panel. Supports single as well

as multiport cards using shared interrupts.
BbLynx.drv Replacement for COMM.DRV.
LynxAPI.dll Enhancement to the Windows Comms API’s

allowing support for more than 9 ports.
Term.exe Terminal program.
EasyCWIN C source code, project files and ready to run.exe

program for an easy to understand Windows

terminal program. Learn how to write Windows

comms apps correctly the easy way.

Chapter 1 Page 3

Serial Solutions PCI VELOCITY / OPTO ISO RS422/485

Serial Solutions For Windows 95.

Windows 95 has an improved communication API and
directly supports up to 255 ports. Our Windows 95 driver supports
the shared interrupt mechanism used on our multiport cards. Serial
Solutions for Windows 95 consists of the following programs: -

SSCards.inf The information file to aid the installation

process "Have Disk....”

Ssmodem.inf Setup file for Serial Solutions modems.

sscardui.dll
ssportui.dll The device manager configuration DLLs and…

ssenum.vxd
ssv485.vxd ...the virtual device drivers providing the shared
ssvel.vxd interrupt handlers and dispatch routines etc for the
ssmult.vxd various Serial Solutions serial cards.
ssm485.vxd

Serial Solutions For Wind ows NT.

Windows NT has an improved communication API and
directly supports up to 255 ports. No extra driver is necessary for
Windows NT to drive multiport cards. Serial Solutions for
Windows NT consists of the following programs: -

Setup.exe Expands into the Control Panel applet and

associated files which allows the configuration of
all ports on Serial Solutions serial cards.

Ssmodem.inf Setup file for Serial Solutions modems.

Complete Documentati o n and T e chnical Bac kup.

We believe in supplying complete documentation with
every package we sell. The Serial Solut ion Software Package is no
exception, it has an attractive manual in an A5 binder, containing

Chapter 1 Page 4

PCI VELOCITY / OPTO ISO RS422/485 Serial Solutions

over 150 pages of in-depth technical detail with comprehensive
indexes and table of contents. We guarantee your Serial Solution
Software package for a full 12 months from purchase. A com plete
technical backup service is available to ensure that you get the
maximum performance out of your investment.

Chapter 1 Page 5

Specifications PCI VELOCITY / OPTO ISO RS422/485

Chapter 2

PCI VELOCITY RS422/485 &

PCI OPTO ISOLATED RS422/485

SPECIFICATIONS

Introduction.

This chapter details the specifications of the PCI Velocity
RS422/485 card and PCI Opto Isolated RS422/485 and explains
how to configure the RS485 Multiplex jumpers present on both
cards. These half-sized cards will work happily in any PCI 2.0 or
greater compliant PC compatible.

Note: The PCI Velocity RS422/485 is identical to the PCI
Optically Isolated (Opto Iso) RS422/485 with regard to software
installation in all operating systems. The only difference is the
presence of the Optical isolation circuitry on the Opto Iso card,
which is detailed below.

General PCI RS422/485 Card Features.

• Two independent 9 pin D RS422/485 Serial ports.

• Reliable communications up to 4000 feet, 1.2 Kilometres.

• 16C750 FIFO provides 64-byte input and 64-byte output buffer

on each port.

• Maximum baud rate of 921,600 Baud (1 Megabaud).

• Wor d length of 5, 6, 7 or 8 bit s .

• Even, Odd, None, Mark or Space parity options.

• 1 start bit always sent.

• 1, (1.5 for 5-bit data word length), or 2 stop bits.

• TXD, RXD, RTS, and CTS signals.

• RS485 TXD/RXD multiplex selectable by jumpers: - either

FULL DUPLEX or HALF-DUPLEX.

• Fully double buffered for reliable asynchronous operation.

• High-speed integrated circuitry ensures operation with fast PC’s

e.g. 333 MHz Pentium II WITHOUT extra wait states.

Chapter 2 Page 6

PCI VELOCITY / OPTO ISO RS422/485 Specifications

• Autogating low level RS485 half duplex (2 wire) control

General PCI RS422/485 Serial P ort Features (cont).

Clock Input: 14.7456MHz
Drivers: SN75174
High Level Voltage: 3.7V typical at 33mA source
Low Level Voltage: 1.1V typical at 33mA source
High Level Current: -60mA max.
Low Level Current: 60mA max.
Receivers: SN75175.
Difftial I/P threshold: 200mV max.
Hysteresis: 50mVolt typical.
Input Impedance: >12K Ohm without terminators.

Autogating.

Multitasking operating systems, like Windows 95,
Windows NT, OS/2 and UNIX, cannot successfully use the RTS

line to control the gating of the PC’s transmitter. Whilst they can
set the RTS line true just before the data transmission starts, they
cannot set the RTS line false quickly enough after the data has
gone. This is due to the time slicing mechanism used by these
multitasking operating systems. The interrupt service routines in
multitasking OS’s have a long latency, i.e. time taken to switch
context from the foreground program to the interrupt routine.
During this time, the first few bytes of the external devices reply to
the PC may be lost since the serial port transmitter is still gated
onto the twisted pair cable.

To overcome this problem, Autogating hardware has been
added to the to the RS422/485 card. This automatically detects the
start of the PC’s data transmissions, and gates the PC’s transmitter
onto the twisted pair cable. It then automatically detects the last
stop bit being sent and gates the port off the twisted pair cable. An
added bonus of RS485 AUTOGATING is that special device
drivers no longer need to be written to use RS485 in any operating

Chapter 2 Page 7

Specifications PCI VELOCITY / OPTO ISO RS422/485

system. To all intents and purposes, it looks just like an ordinary
RS232 COM port to the host PC. Autogating for half duplex
operation is a necessity for Windows 95, NT and the forthcoming
Windows 98 (Memphis) and Windows NT 5.

Optical Is olation.

The PCI Opto Iso RS422/485, as mentioned above is
identical in installation procedure to the PCI Velocity RS422/485.
In addition, it also has optical isolation circuitry on board that
allows protection of:

1500 Volts DC

± 1000 Volts AC

This isolation present on board also allows greater
protection from current surges, lightning strikes to both the card
itself and the PC, and also it improves noise immunity by isolating
the PC from the cards transmit ground.

Chapter 2 Page 8

PCI VELOCITY / OPTO ISO RS422/485 Specifications

Figure 2-1. PCI VELOCITY RS422/485 Card Layout.

P
O
R
T
#1

TX/RX1+
TX/RX1­TX/RX2­TX/RX2+

P
O
R
T
#2

MULTIPLEX

RS485

RS485 Multiplex jumper block

PCI VELOCITY RS422/485 Specifications:

Dimensions: 5 x 3 in, 120 x 85 mm
I/O Connection: Serial Port 1: 9 pin Male D type.

Serial Port 2: 9 pin Male D type.

Weight: 95g

Chapter 2 Page 9

Specifications PCI VELOCITY / OPTO ISO RS422/485

Figure 2-2. PCI Opto Iso RS422/485 Card Lay out.

P
O
R
T
#1

TX/RX1+
TX/RX1­TX/RX2­TX/RX2+

P
O
R
T
#2

MULTIPLEX

RS485

RS485 Multiplex jumper block

PCI Opto Iso RS422/485 Specifications:

Dimensions: 5 x 3 in, 126 x 99 mm
I/O Connection: Serial Port 1: 9 pin Male D type.

Serial Port 2: 9 pin Male D type.
Weight: 100g
Optical Isolation 1500 Volts DC

± 1000 Volts AC

Chapter 2 Page 10

PCI VELOCITY / OPTO ISO RS422/485 Specifications

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Configuring The PCI RS422/485 Cards.

PCI cards require no hardware configuration for IRQ and
address allocation - this is done automatically at start up by the PC.
However, the PC Velocity RS422/485 and PCI Opto Iso RS422/45
both have two sets of jumpers for configuration of RS485
multiplex modes, how to configure these jumpers is shown below.

RS485 Multiplex Jumper Settings.

The RS485 Multiplex jumper block, indicated on Figures
2-1 and 2-2, is shown below with default settings of no jumpers
present (both ports full duplex).

Where:
TX/RX1+ and TX/RX1- control port 1 RS485 multiplexing.
TX/RX2+ and TX/RX2- control port 2 RS485 multiplexing.

Chapter 2 Page 11

Specifications PCI VELOCITY / OPTO ISO RS422/485

Port 1 With Full Duplex Settings.

•

Both jumpers left unconnected (not shorted).

Port 1 With Half Duple x Se ttings.

• Both jumpers shorted, causing the RXD- & TXD- and the

RXD+ & TXD+ signals to short together at the 9-pin
connector. The multiplex jumpers should only be set for
RS485 Half Duplex operation, when one twisted pair is used to
interconnect both transmit and receive lines.

NOTE: Any changes to RS485 Multiplex Operation must be
accompanied with appropriate changes t o the driver software; see
the Chapter 3 - "PCI Velocity RS422/485 Software Configuration"
for more details.

For further details on the RS422 and RS485 standard, pinouts, half
duplex and full duplex RS485 systems, wiring diagrams and
optional grounding diagrams refer to Chapter 4 - "Optional

RS422/485 Operation."

Chapter 2 Page 12

PCI VELOCITY / OPTO ISO RS422/485 Specifications

Hardware Installation.

STEP 1: Before the PC card can be installed the power to the PC
MUST be switched OFF, and to ensure extra safety, the power
lead removed from the PC.

STEP 2: Remove the PC case.

Step 3 - Removing Blanking Cover

Choose an empty expansion slot. Remove
the blanking cover protecting the slot on
the PC back panel. KEEP the blanking
cover screw safely for later.

Step 4 - Inserting The PCI Serial Card.

Now insert the PCI Serial card in the slot.
Be careful to ensure that the gold plated
PCB fingers fits neatly into the expansion
connector. Press down firmly but evenly
on the top of the PCI Serial card

STEP 5: The connectors should fit neatly through the slot’s
aperture to the outside world.

Chapter 2 Page 13

Specifications PCI VELOCITY / OPTO ISO RS422/485

STEP 6: Now replace the system unit’s cover by car ef ully sliding it
down and back over the system unit. Replace the cover mounting
screws.

STEP 7: After attaching all the monitor and keyboard cables,
power up the PC. Do not forget the mains power cable! The PC
should then power on in the normal way.

Problems!

If the system fails to power up normally, check the following:

i.) Ensure that the PCI Serial card is installed correctly.
ii.) Ensure that other cards in the PC have not been upset.
iii.) Ensure that the power is connecte d and the PC is switched ON!

If all these have been checked and the PC still does not
power up then inspect the area surrounding the card to ensure that
any potentially harmful bits of metal etc. are not present, if the
problem persists ask your dealer to check the card or contact the
HELP line as given on Intro. Page 2.

Chapter 2 Page 14

PCI VELOCITY / OPTO ISO RS422/485 Software Configuration

Chapter 3

PCI VELOCITY RS422/485 &

PCI OPTO ISOLATED RS422/485

SOFTWARE CONFIGURATION

GUIDE

Introduction.

This section contains the installation procedures of the PCI
VELOCITY RS422/485 card, with the Windows 95 & 98,
Windows NT DOS, and Windows 3.x operating systems.

As previously noted, the install procedure for the Velocity
and Opto Isolated PCI RS422/485 cards are the same, with the
only difference being the reported card name in Windows 95 & 98
and NT 4.0; instances where this occurs wil l be clearly labeled.

The setup procedures in this chapter assume that your PC
has only one serial port present.

Installing Ports In Microsoft Windows 95 & 98.

Although covering the installation of the PCI Velocity
RS422/485 the Windows 95 operating system, the procedure is
also valid, with only minor differences, in the Windows 98
Operating System. The Windows 95 environment now supports up
to 255 standard serial ports, RS232, RS422, RS485 etc.

To obtain a trouble free mix-and-match of the COM ports:

• Switch off your computer, insert your PCI RS422/485 card into

a free PCI slot, as described in the section "Hardware
Installation" in Chapter 2, and switch your computer on again.

• During the booting process, Windows 95 will detect the PCI

Velocity RS422/485, but will display it simply as a "PCI
CARD", and you will briefly see a message box to this effect.

Chapter 3 Page 15

Software Configuration PCI VELOCITY / OPTO ISO RS422/485

Opto Iso users, this entry

• Windows will then display the "Update Device Driver Wizard",

which asks you to “insert any disk which came with the PCI
card”. Insert the Windows 95 installation disk into an
appropriate drive and click 'Next'.

• The Wizard should then display the following:

• Click Finish.

• A "Copying Files…" window should now appear. Click 'OK'

when it asks you to insert the disk.

Chapter 3 Page 16

will appear as:

PCI Opto RS422/485 rev
2

PCI VELOCITY / OPTO ISO RS422/485 Software Configuration

• After copying the file, Windows 95 will then detect each of the

serial ports in turn and install them as communications ports.

When the "Device Manager" is viewed the PCI R422/485
card will appear under the "Multi-function adapters" branch as
either PCI Velocity RS422/485 card or PCI Opto Iso RS422/485
(parent device). Also, two Velocity RS485 Ports will appear under
the "Ports (COM & LPT) branch" (child device).

For most users who have 4 or less COM ports the new
ports will appear as COM5 and COM6, as pictured below; for
users with more than 5 COM ports the new ports will appear as the
first available COM ports.

PCI Velocity RS422/488 users:

PCI Opto RS422/488 users:

Chapter 3 Page 17

Software Configuration PCI VELOCITY / OPTO ISO RS422/485

PCI Velocity RS422/485 Car d Sett i ngs In Windows 95
& 98.

• Select the PCI Velocity RS422/485 card from the "Multi-

Function Adapter" entry in Device Manager serial and click

on properties to view the cards general properties; clicking on
the Serial Solutions tab produces:

Opto users, this entry will
appear as:

PCI Opto RS422/485
Card Properties.

The I/O address and interrupt
are assigned to the card by t he
"Plug and play" system of the
PC. These values CANNOT
be changed with the current
version of the driver.

In this window, the COM port assignment may be changed,
simply by selecting a new COM port value from the pull down
menu relevant to the port. However, COM port usage other than
those for the PCI Velocity RS422/485 card itself are not checked,
so it is advisable to first check which COM ports are in use - port
availability can be checked by viewing the Device Manager:

Chapter 3 Page 18

PCI VELOCITY / OPTO ISO RS422/485 Software Configuration

All COM ports present will be listed under the entry "Ports
(COM & LPT)." T he above screenshots indicates that COM2 - 4

and COM7 and above are not installed, and therefore may be used.

PCI RS422/485 Port Settings I n Wind ows 95 & 98.

Double clicking on a Velocity RS485 Port entry from the
entry "Ports (Com & LPT)" branch in Device Manager will the
display general properties window for the selected port (in this
case COM5).

• Selecting the Port Settings tab produces:

Settings available in this window are:

1. Baud Rate - determines the baud rate at which the

selected port operates, the maximum value available is
dependant upon the Maximum Baud Rate Setting (see
below.)

2. Data Bits.

3. Parity.

Change to suit remote device.

4. Stop Bits.

5. Flow Co ntrol.

6. Maximum Baud Rate Setting - four values are

available, which selects the maximum baud rate at
which the port may operate. Table 3-1, below, indicates

Chapter 3 Page 19

Software Configuration PCI VELOCITY / OPTO ISO RS422/485

Selectable

Baud

Rates

the ranges of baud rate values available at the
Maximum Baud Rate Settings.

Table 3-1 Maxi m um B aud Rate Settings.

Maximum Baud R a te

115200 230400 460800 921600

50 100 200 400

75 150 300 600
110 220 440 880
150 300 600 1200
300 600 1200 2400
600 1200 2400 4800

1200 2400 4800 9600
1800 3600 7200 1440
2000 4000 8000 16000
2400 4800 9600 19200
3600 7200 14400 28800
4800 9600 19200 38400
7200 14400 28800 57600

9600 19200 38400 76800
19200 38400 76800 153600
38400 76800 153600 230400
57600 115200 230400 460800

115200 230400 460800 921600

Note: Many serial comms applications will not actually
register the ports as running at baud rates of above 115200.

7. Restore Defaults - when clicked, resets the selected

COM port to the following values:
Baud Rate: 9600
Data Bits: 8
Parity: None
Stop Bits: 1

Chapter 3 Page 20

PCI VELOCITY / OPTO ISO RS422/485 Software Configuration

Flow Control: Xon / Xoff
Maximum Baud Rate Setting: 115,200

• Clicking on the Serial Solutions tab will display:

Settings available in this window are:

1. FIFO Setting s.

• Ena ble F IFO - t urns the sel ected ports FIFO buffer

on or off. It is strongly recommended that the FIFO
for both ports is left enabled.

• Exten d FI FO - when checked, extends the selected

ports FIFO buffer from 16 to 64 bytes.

• Receive B uffer - These settings allow the selection

of a receiver FIFO trigger setting. Selecting a low
value will allow the interrupt to be serviced quicker,
which is good for slow machines. If you have a fast
machine, setting a high value will give you more
time for multi-tasking operations.

• Transmit Buffer - These settings allow the selection

of a tr an smitte r FI FO tr ig ger setti ng. Sel ect ing a low
value will send fewer data-bytes per interrupt, and
this is recommended if you are communicating to a

Chapter 3 Page 21

Software Configuration PCI VELOCITY / OPTO ISO RS422/485

slower machine. Selecting a high value will send
more data-bytes per interrupt, and will give more
time for multi-tasking operations.

2. Automatic Hardware Flow Control. One of two

options may be selected:

• Off (Default) - This will turn off automatic flow

control. (If you have no data transfer problems then
selecting this option is fine.)

• RTS/CTS - This will use the RTS and CTS lines

for automatic hardware flow control.

3. 485 Mode offers the options:

• Half Duplex / Full Duplex(default) - are used in

conjunction with the RS485 Multiplex Jumper
Settings.
NOTE: These software settings must match the
RS485 Multiplex Jumper configuration, as
described in the section "RS485 Multiplex Jumper
Settings" in Chapter 2, to ensure accurate and error
free data transmission.

• CTS Hold True, determines whether the CTS

handshake signal is INPUT from the external serial
device or is permanently forced true on the card.
The serial ports own RTS OUTPUT handshake
signals are always taken out to the serial port
connector.

4. Restore - when this button is clicked the settings in the

current window will be reset to the default values of:
Enable FIFO: On (Checked)
Extend FIFO: Off (Unchecked)
Receive Buffer: 3rd from left.
Transmit Buffer: 16
Automatic Hardware
flow Control: Off
485 Mode: Full duplex.

Chapter 3 Page 22

PCI VELOCITY / OPTO ISO RS422/485 Software Configuration

Configuring Ports In Microsoft Windows NT 4.0.

Microsoft Windows NT Provides built in support for 255
standard serial ports. To setup your PCI RS422/485 serial card you
should follow these steps. Please note that to change any kind of
hardware configuration under Windows NT you must be logged in
as a user with Administrator level privileges, if you do not have
these please contact your system administrator.

Software Installation.

Insert the PCI Velocity RS422/485 into your PC, as
described in chapter 2, and restart. Place the supplied floppy disk
titled "Serial Solutions for Windows NT" in a suitable drive and
from the Start Menu choose Run and enter a:\setup (where a:
is the path to the floppy drive with the installation disk).

• InstallShield will then install the driver software automatically -

it will then copy the necessary files and start itself. This
automatically detects your new PCI serial card(s) and does not
require any further system restarting.

Chapter 3 Page 23

Software Configuration PCI VELOCITY / OPTO ISO RS422/485

Opto Iso users, these

Card

Examining Card Configuration.

Go to Control Panel (Start/Settings/Control Panel) and
double click on Serial Solutions PCI:

You will be presented with a Serial Solutions PCI Port
Configuration window:

Chapter 3 Page 24

entries under card will
appear as:

PCI Opto RS422/485

PCI VELOCITY / OPTO ISO RS422/485 Software Configuration

Configuring Port s.

To view the settings of a port, select it and click on
settings, and then click on the resources tab:

Settings available in this window are:

Settings available in this window are:

1. Baud Rate - determines the baud rate at which the

selected port operates, the maximum value available is
921,600 (1 Megabaud.) Note: Many serial comms
applications will not actually register the ports as
running at baud rates of above 115200.

2. Data Bits.

3. Parity.

Change to suit remote device.

4. Stop Bits.

5. Flow C o ntrol.

Chapter 3 Page 25

Software Configuration PCI VELOCITY / OPTO ISO RS422/485

6. Advanced - see the section below, titled "Advanced

Port Settings."

7. Restore Defaults - when clicked, resets the selected

COM port to the following values:

Baud Rate: 9600
Data Bits: 8
Parity: None
Stop Bits: 1
Flow Control: Hardware

Advanced P ort Se ttings.

When the Advanced button of Port Settings is selected the
following dialogue is displayed:

Settings available in this window are:

1. FIFO se t tings.

• Use FIFO Buffers - turns the selected ports FIFO

Chapter 3 Page 26

PCI VELOCITY / OPTO ISO RS422/485 Software Configuration

buffer on or off. It is strongly recommended that the
FIFO for both ports is left enabled.

• Receive B uffer - These settings allow the selection

of a receiver FIFO trigger setting. Selecting a low
value will allow the interrupt to be serviced quicker,
which is good for slow machines. If you have a fast
machine, setting a high value will give you more
time for multi-tasking operations.

• Transmit Buffer - These settings allow the

selection of a transmitter FIFO trigger setting.
Selecting a low value will send fewer data-bytes per
interrupt, and this is recommended if you are
communicating to a slower machine. Selecting a
high value will send more data-bytes per interrupt,
and will give more time for multi-tasking
operations.

• Use Extended FIFO Buffers - when checked,

extends the selected ports FIFO buffer from 16 to
64 bytes.

2. Automatic Hardware Flow Control. One of three

options may be selected:

• Off (Default) - This will turn off automatic flow

control. (If you have no data transfer problems then
selecting this option is fine.)

• RTS/CTS - This will use the RTS and CTS lines

for automatic hardware flow control.

3. 485 Mode offers the options:

• Half Duplex / Full Duplex(default) - are used in

conjunction with the RS485 Multiplex Jumper
Settings.
NOTE: These software settings must match the
RS485 Multiplex Jumper configuration, as
described in the section "RS485 Multiplex Jumper

Chapter 3 Page 27

Software Configuration PCI VELOCITY / OPTO ISO RS422/485

Settings" in Chapter 2, to ensure accurate and error

free data transmission.

• Force CTS True, determines whether the CTS

handshake signal is INPUT from the external serial
device or is permanently forced true on the card.
The serial ports own RTS OUTPUT handshake
signals are always taken out to the serial port
connector.

4. Defaults - When clicked this button resets the advanced

properties to the followed settings:

Use FIFO Buffers: On (checked)
Transmit Buffers: 1
Receive Buffers: 8
Use Extended FIFO: Off (Unchecked)
Automatic Hardware
Flow Control: Off
485 Mode: Full Duplex

Uninstalling Serial Solutions PCI.

To uninstall Serial Solutions PCI:

• From Control Panel, open the Add/Remove Programs applet,

then close the Control Panel.

• Select from the list Serial Solutions PCI.

• Click the Add/Remove button.

Windows NT will then uninstall the Serial Solutions PCI applet
without the need for restarting.

Chapter 3 Page 28

PCI VELOCITY / OPTO ISO RS422/485 Software Configuration

Configuring Ports I n Wind ows 3. x

The Windows 3.x installation procedure consists of two
steps after the PCI RS422/485 card is inserted:

1. Determining the resources that the PCI RS422/485 card has

claimed.

2. Informing Windows 3.x of those resources.

Determining PCI RS422/485 Resources.

• Insert the card into a PC, as described in Chapter 2.

• Run BBCARDS.EXE, from the supplied DOS utility disk titled

"Serial Solutions Utility Disk" by typing the following:

%@4'-@&&'%6(7

Where A:\ is the drive containing the supplied disk.

BBCARDS.EXE will return a string that looks similar to
the following (values contained in the string may differ in
individual PC’s due to resource availability):

Velocity users:

GEVHMWSRFYWHIZMGIJYRGXMSR
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• Note down IRQ and I/O address, which in this case are:

The IRQ = 11

The I/O address = 0140

Chapter 3 Page 29

Software Configuration PCI VELOCITY / OPTO ISO RS422/485

Windows 3.x Software Installati on.

Place the supplied Serial Solutions for Windows 3.x disk in

a suitable drive. From File Manager choose ‘Run’ and enter
a:\setup (where a: is the path to the floppy drive with the
installation disk).

• Click OK, the Setup Program Main Screen is displayed:

By default, all component options will be installed,
selecting the "Del All" button will select all installed components
for deletion and "Add All" chooses all uninstalled components for
installation; options may not be changed when the components are
installed. For further details on the Component Options consult the
README.TXT file on the supplied disk.

If only logical ports COM1 to COM9 are to be used then
de-select the Comms API library option in the "Install" column.
This library is only necessary to allow the use of logical ports
greater than COM9 e.g. COM10, COM11 et c.

Chapter 3 Page 30

PCI VELOCITY / OPTO ISO RS422/485 Software Configuration

• When you have made your choice of Component Options click

Continue and when the setup program has finished select the
Done button.

Note: If the Serial Port driver options has been selected, af ter the

setup program has finished, Windows will display a restart
message - answer Yes and Serial Solutions will be ready to run
upon Windows restarting.

Serial Port Installation.

• From Main, select Control Panel:

• Click on S erial P ort s:

Chapter 3 Page 31

Software Configuration PCI VELOCITY / OPTO ISO RS422/485

The following dialogue will be displayed:

To add a COM port:

• Click on the add button and a Window similar to the following

will be displayed:

• In Standard Settings:

• In the COM Base field, enter the value 0140.

Note: COM ports are defined with an i/o address range,
which in this case, begins at 0140 and all subsequent
ports have an i/o address that is 8 higher than the
previous. i.e. if COM2 has an address of 0140h, then
COM3 has an address of 0148h.

• In t he IRQ fiel d, enter the value 11.

Chapter 3 Page 32

PCI VELOCITY / OPTO ISO RS422/485 Software Configuration

Note: The values used in the above section were those

returned by the BBCARDS program, as described in the

above section.

When you have finished, click on OK. A rest art message

will be displayed; to save time only restart when both ports

have been added and correctly configured.

• Repeat the above process to add the second COM port of the

PCI RS422/485, the COM base will be 0148; the IRQ value
will remain the same. After adding the remaining COM port
the COM Ports Window will look similar to the following:

Configuring The COM Por ts.

• From the COM Ports window choose the port that you wish to

configure and click on Settings - the following dialogue will
be displayed:

Chapter 3 Page 33

Software Configuration PCI VELOCITY / OPTO ISO RS422/485

Note: A port that has been added has the default values of:

Baud Rate: 9600

Data Bits: 8

Parity: None

top Bits: 1.0

Flow: None

Change the communications Settings in the COM Ports to
match the baud rate, parity settings etc. of the remote serial device.

Deleting Ports in Windows.

The Delete button can be used to discard the entries of
ports that have been removed from the system.

Note. Never try to leave out a serial port number when
using the delete button, because Windows may automatically shift
serial port numbers which results in a mis-match of settings in the
Serial Ports Applet (COM1-COM4 only).

Re starti ng Windows.

Whenever certain values have been entered or changed in
the hardware settings window, a message prompting to restart
Windows will appear. Only after having made ALL the necessary
changes restart Windows so that the new settings come into effect.

Chapter 3 Page 34

PCI VELOCITY / OPTO ISO RS422/485 Software Configuration

Configuring Port s I n DOS.

The DOS installation procedure consists of two steps after
the PCI RS422/485 card is inserted:

1. Determining the resources that the PCI RS422/485 has claimed.

2. Informing the Serial Solutions DOS device driver of those

resources.

Determining PCI RS422/485 Resources.

• Insert card into PC, as described in Chapter 2.

• Run BBCARDS.EXE, from the supplied DOS utility disk titled

"Serial Solutions Utility Disk" by typing the following:

%@4'-@&&'%6(7

Where A:\ is the drive containing the supplied disk.

BBCARDS.EXE will return a string that looks similar to
the following (values contained in the string may differ in
individual PC’s due to resource availability):

Velocity users:

GEVHMWSRFYWHIZMGIJYRGXMSR
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Opto Iso u sers:

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• Note down IRQ and I/O which in this case:

The IRQ = 11

The I/O address = 0140

Chapter 3 Page 35

Software Configuration PCI VELOCITY / OPTO ISO RS422/485

NEWCOM.SYS Parameters.

The NewCOM.SYS device driver included with the PCI
RS422/485 driver software is used to set up the card in DOS and
has the following syntax:

NEWCOM.SYS /A port address, /I IRQ,range /B number buffer
/S buffer /H hardware handshake

Where /A port address specifies COM port number followed by a

hexadecimal address in the form /Ax,y where x is COM

port range and y is I/O address.

/I IRQ, range specifies card interrupt and COM port range. The

COM port range specifies the COM port(s). Range may be a

single port OR a ra nge of por ts .

/B number buffer is used to set the number of pairs of

buffers to be allocated to ports and is a decimal number in

the range 1-maxport.

/S buffer Set size of all buffers in bytes, buffer is rounded

to the nearest power of 2 and must be a decimal number in

the range 32 to 32768. For any serial port opened two

buffers of size buffer are allocated, one for input and the

other for output.

/H hardware handshake selects which hardware handshake

type to use on the specified ports. This is used in the

following manner: /H range, hs where range specifies the

COM port or ports and hs selects handshake type.

Handshake types available are:

Type 0 RS232 DTR/CTS - The PC only transmits

Chapter 3 Page 36

when CTS is input true. When the PC is able to

PCI VELOCITY / OPTO ISO RS422/485 Software Configuration

receive its sets DTR output true. The DSR and
DCD inputs are ignored. The RTS output line
is set true just in case the external serial device
needs a true signal.

Type 1 RS422 RTS/CTS - The PC only transmits when

CTS is input true. When the PC is able to receive
its sets RTS output true. The DSR and DCD
inputs are ignored. The DTR output line is set
true just in case the external seri al device needs a
true signal.

Type 2 RS485 Half duplex - Before any data is sent the

PC sets RTS true, after the last byte in the buffer
has been sent the PC sets RTS fal se. RT S is used
as a transmit gating control. The CTS, DSR and
DCD inputs are ignored. The DTR output line is
set true just in case the external serial device
needs a true signal.

Type 3 RS485 Send only - This is a half duplex, transmit

only handshake. The PC transmits whenever it
wishes, it cannot receive any data. The CTS,
DSR and DCD inputs are ignored. The RTS
output line is set true just in case the external
serial device needs a true signal .

Type 4 3 Wire Handshake - Really no handshake at all

since the PC transmits irrespective of the
handshake lines. The 3 wires are TxD, RxD and
Ground, no other lines are required. Thus the
CTS, DS R and D CD in put s ar e ig nor e d. T he RT S
and DTR output lines are set true just in case the
external serial device needs a true signal.

Chapter 3 Page 37

Software Configuration PCI VELOCITY / OPTO ISO RS422/485

Note: If hardware handshaking is not specified in the

NEWCOM.SYS parameters, type 4, 3 Wire
Handshake is sele cted automatically.

Configuring And Inst all ing NEWCOM.S YS

To lo ad the Ser ial Solu tion s for DOS d evice dr iver an en try
needs to be added to the CONFIG.SYS file. Any simple text editor,
EDIT f or e xa mpl e, can ed it the C O NFI G.S Y S fi l e f or ex am pl e. T h e
ins talla tion pr ocedu re gi ven bel ow is for a P CI RS4 22/4 85 as CO M
5 - COM6.

The parameter required by the NEWCOM.SYS driver are
those returned by the BBCARDS.EXE application earlier. A brief
explanation for the parameters required by NEWCOM.SYS follows:

Port Address.

/A5-6,0140

COM ports 5 and 6 are defined, with an i/o address range
that begins at 0140h with the next port having an i/o address that is
8 higher than the previous. i.e. COM5 has an address of 0140h,
therefore COM6 will have an address of 0148h.

IRQ, Rang e.

/I 11,5-6

11 is the IRQ and since the COM port range is COM5 ­COM6 range is entered as 5-6.

Number Buffer.

/B6

Six buffers are defined, though only four ports are in use ­this is because buffers in DOS are assigned in a sequential order
from COM1. Since the PCI Velocity RS422/485 has been assigned

Chapter 3 Page 38

PCI VELOCITY / OPTO ISO RS422/485 Software Configuration

COM port values of 5 to 6, all pr eceding COM ports, must have
buffers assigned to them also.

Bu ffer S ize.

/S512

Buffer size set to 512 bytes.

Hardware Handshaking.

/H,4

Type 4, 3 Wire Handshake selected for all ports. Type 4, 3
Wire Handshake selected for all ports.

Modifyi ng C ommand Line Parameters.

When "assembled" the NEWCOM.SYS command line

looks like…

DEVICE=NEWCOM.SYS /A5-6,0140 /I 11,5-6 /B8 /S 512 /H,4

…and should be entered into the CONFIG.SYS file. Once you are
sure that these parameter s have been entered correctly, restar t your
PC and your PCI RS422/485 should be ready to use immediately.
Sample terminal applications are provided on "Serial Solutions
Disk 1 & 2" enabling communications to be established to your
peripherals quickly and easily.

Chapter 3 Page 39

RS422/485 Information PCI VELOCITY / OPTO ISO RS422/485

Chapter 4

ADDITIONAL RS422/485

OPERATION

The RS422 Standard.

The RS422 standard defines a serial communications
standard. RS422 is a high speed and/or long distance data
transmission. Each signal is carried by a pair of wires and is thus a
differential data transmission system. Over distances up to 40 feet
the maximum data rate is 10 Megabits per second, and for distances
up to 4000 feet the maximum data rate is 100 Kilobytes per second.
A 120-Ohm resistor should be used to terminate the receiving end
of the line. It is generally used between one transmitter receiver pair
to ONLY one other transmitter receiver pair, but each output can
drive up to 10 receivers.

RS422 Standard

1 Driver up to 10 Receivers

Line Length Max Data Rate

40 Feet = 12m 10 Mbits/sec

400 Feet = 122m 1 Mbits/sec

4000 Feet = 1219m 100 Kbits/sec

880 880

(

6

The RS485 Standard.

The RS485 standard is similar to the RS422 standard upon
which it is based. The main difference is that up to 32 transmitter
receiver pairs may be present on the line at one time. A 120-Ohm

Chapter 4 Page 40

PCI VELOCITY / OPTO ISO RS422/485 RS422/485 Information

6

6

resistor should be used to terminate either end of the main line. If
more than one device may transmit data, the RTS line is used as
transmit enable signal, so preventing contention between talkers.

RS485 Standard

Up to 32 Driver/Receiver Pairs

Line Length Max Data Rate

40 Feet = 12m 10 Mbits/sec

400 Feet = 122m 1 Mbits/sec

4000 Feet = 1219m 100 Kbits/sec

((

6

Terminating Impedance’s.

RS422 and RS485 lines should be terminated at the end of
the main branch of the RECEIVER, in the cables characteristic
impedance. These terminating impedance’s stop echoes caused by

the serial data being reflected back at the cable ends. It is not
necessary to terminate the transmitter end of the twisted pair.

The AT Dual Port RS422/485, Opto Isolated AT Dual Port
RS422/485 and AT Velocity RS422/485 cards have the correct 120
Ohm (nominal) terminating resistors for the RXD twisted pair line
and the CTS twisted pair line fitted on the RS422/485 card for both
the serial ports on the card.

There is no need to add any more at the PC end.

The terminating impedance’s shown later in the wiring
diagrams of Figure 4-1, Figure 4-2, Figure 4-4 & Figure 4-6 are
automatically provided by the on board resistors and do not have to
be added by the user.

Chapter 4 Page 41

RS422/485 Information PCI VELOCITY / OPTO ISO RS422/485

Fail Safe Open Circuit Detection.

Open circuit is when there are no drivers on the circuit. This
occurs by design in party line multi driver/receiver systems and
unintentionally when the twisted pair line is accidentally cut or
disconnected or the transmitting device fails. In RS485 party line
systems there are extended periods of time when none of the many
possible talkers are gated onto the bus. This is known as the line
idle state and occurs when all the driver outputs are in the high
impedance state. The lines float, perhaps being pulled to the high or
low state by noise or other voltages on the line.

Without fail safe open circuit detection false start bits are
detected by the receivers, either corrupting good communications
or causing noise to masquerade as good data.

The on board fail safe open circuit detection causes the
receiver to go to a known, pre-determined state and prevents false
start bits and bad data being detected during open circuits.

Fail Safe Shor t Cir cuit Protection.

Short circuits are when the two lines of a twisted pair are
connected together. This occurs due to either accidental damage to
the cable or due to failure of one or more transmitter/receivers on
the line. The short circuit condition is dangerous since damage to
the receiver may occur and communication may be corrupted or
prevented.
The on board fail safe short circuit detection prevents the line
impedance from going to zero and thus protects the inputs of
receivers and the outputs of drivers.

RS422 Operation.

Generally, in RS422 systems all 8 signal lines from the 9
pin D connector participate in the data transfer sequence, thus 4
twisted pair cables are used. One twisted pair carries the TXD data
outwards, one pair brings the RXD data inward, another pair carries
the RTS handshake outwards and the fourth pair brings the CTS

Chapter 4 Page 42

PCI VELOCITY / OPTO ISO RS422/485 RS422/485 Information

handshake inwards. There is no need to carry the ground from one
device to another.

This RS422 arrangement allows data to be transmitted and
received simultaneously since each signal has its own data cable
pair. In addition, the receiver can set RTS true so telling the
transmitter on its CTS input that the receiver is ready to accept data.
In this way, no data will ever be transmitted when the receiver is
unable to accept it, due to a full input buffer etc. And so no data
will be lost.

RS422 Serial Port Cables.

Use screened twisted pair Belden cable 9729 and 9829, L
type 2493 and 2919 or IBM Part No 4716748 cable to make the
RS422 connection. Unscreened Belden type 8795 may also be used
in less noisy environments.

The on board resistor networks terminat e the receiving end
of the twisted pair cable in its characteristic impedance.

Figure 4-1. Serial Port 1 To Other PC Cable.

7)6-%043687MHI 3XLIV4'7)6-%043687MHI
4MR*IQEPI('SRRIGXSV 4MR*IQEPI('SRRIGXSV

Chapter 4 Page 43

RS422/485 Information PCI VELOCITY / OPTO ISO RS422/485

Note:

i.) Receiver ends terminated in characteristic impedance

ONBOARD resistor networks.

ii.) USE BELDEN TYPE 9729 etc. see above.
iii.) RS485 Gating & Multiplex Jumpers as Factory Set.

RS485 Operation.

The RS485 standard is intended for up to 32 driver receiver
pairs on the bus. The line drivers used in the Serial Solutions
RS422/485 card are designed to work correctly in both RS422 and
RS485 systems. The main difference therefore is in how the system
is implemented. Though the card uses a 9 pin D connector, in
general, not all the lines are used for RS485 systems. The RTS+/­and CTS+/- lines, though driven by the card, are usually not
connected. In two wire, Half-Duplex configurations the TXD+ line
is connected to the RXD+ whilst the TXD- line is connected to the
RXD-, only one pair of twisted wire cable is used in RS485 Half
Duplex communications.
The hardware handshaking performed by the CTS+/- and
RTS+/- lines in RS422 systems are handled by a software protocol
in RS485 systems. In situations where more than one device may
transmit data on the shared data line, each cards RTS line is used as
a gating signal to enable the TXD driver only when that card needs
to transmit data, i.e. set TXD GATE or AUTO jumper. This
mechanism prevents bus contention caused by multiple transmitters
holding the line in opposing states. Revision 3 and higher versions

of this card have a facility which automatically “gates” the RTS
line, thus enabling the transmitter independently of any software.
This “Auto gating” is described in more detail in the previous 485
half duplex section
The three wiring schemes given described below are: -

i.) RS485 One Talker Many Listeners (HALF DUPLEX)
ii.) RS485 Many Talkers Many Listeners (HALF DUPLEX.)
iii.) RS485 Many Talkers Many Listeners (FULL DUPLEX.)

Chapter 4 Page 44

PCI VELOCITY / OPTO ISO RS422/485 RS422/485 Information

RS485 Cable.

For best noise immunity use twisted pair cables to make the
RS485 connection. In Half Duplex wiring only 1 twisted cable pair
is needed. Two twisted pair cables are needed for Full Duplex
communications.

Use screened twisted pair Belden cable 9729 and 9829, UL
type 2493 and 2919 or IBM Part No 4716748 cable to make the
RS485 connection. Terminate the twisted pair cable at either end in
its characteristic impedance, which for the Belden 9729 cable is
120 Ohms. Unscreened Belden type 8795 may also be used in less
noisy environments.

RS485 One Talker - Many Listeners, Half Duplex.

There are several schemes for connecting RS485 devices
depending on the characteristics of the system. In many cases there
will be only one device, which can transmit, data and all the others
simply listen to it. This scheme is used for theatrical lighting
intensity control in the DMX512 standard. This is shown in Figure
4-2, below. For the talker the RS485 TXD GATE jumper should
remain in the factory set position, i.e. transmitter is always enabled.
There is NO multiplexing of the TXD and RXD lines. Data is only
flowing one way, from PC outwards, and is thus a Half-Duplex
configuration, only one twisted pair cable is needed.

Figure 4-2. RS485 1 Talker Many Listeners.

Note: The Receiver end of MAIN line terminated in

characteristic impedance by ONBOARD resistor networks, stubs

Chapter 4 Page 45

RS422/485 Information PCI VELOCITY / OPTO ISO RS422/485

+RXDn-1

-RXDn-1

+TXDn-1

-TXDn-1

off the main not terminated.

In the above scheme, one RS485 device is talk only, it
transmits data, but it does not receive any. The other RS485 devices
are receive only, they do not transmit any data at all. Figure 4-3
gives the RS485 Gating jumper settings.

Figure 4-3 Half Duplex Settings of RS485 Multiplex

• Both jumpers shorted, causing the RXD- & TXD- and the

RXD+ & TXD+ signals to short together at the 9-pin connector.

RS485 Many Talkers- Many Listeners, Half Duplex.

Another popular RS485 layout is for multiple talkers and
multiple listeners. This is shown in Figure 4-4, below. This is also
known as "party line" transmission. It is imperative to have some
method of preventing two devices trying to drive the data lines at
the same time. The normal method is to use the RTS line as a talk
enable. The RTS line should go true immediately prior to the data
transmission and go false immediately after the last byte in the
stream is sent. See Figure 4-3 for jumper settings.

Figure 4-4. RS485 Many Talkers & Listeners. Half Duplex

TXD1+
TXD1-

120

W

-RXD1
+RXD1

+RXD2

-RXD2
+TXD2

-TXD2

+RXD3

-RXD3
+TXD3

-TXD3

+TXD n

120

W

-TXD n

-RXDn
+RXDn

Note: BOTH ends of MAIN line terminated in characteristic
impedance, stubs off main line not impedance, since both ends

Chapter 4 Page 46

PCI VELOCITY / OPTO ISO RS422/485 RS422/485 Information

receive. The twisted pair ends are wired to both RXD+ & TXD+
and RXD- & TXD- at each RS485 device!

RS485 Many Talkers- Many Listeners, F ull Duplex.

The RS485 many talkers, many listeners, Full Duplex
system can be used when all the RS485 devices have separate
Transmit and Receive channels. There is NO multiplexing of the
TXD and RXD signals on the same device. This system is
especially useful when there is no flow control avail able on t he PC,
usually due to the use of a third party communications program that
prevents the use of the RTS signal as a "transmit enable" control,
via the TXD GATE jumper. It can be used in the following
situations:­ a) The PC is connected to only ONE RS485 device.
b) The PC is communicating with several RS485 devices that
are each able to recognize and respond to their own unique address.

The RS485 devices only drive their TXD lines when they
are responding to requests from the PC to send data. In effect, the
RS485 device’s address and the command it receives is used to
control access to the devices T XD channel.

This is a Full Duplex system. Two twisted pair cables are
required. One twisted pair, is the PC’s TXD channel, it carries the
data sent from the PC’s TXD outputs to the RXD inputs of each of
the RS485 devices. The second twisted pair, is the Devices TXD
channel, it carries the data sent from each of the devices’ TXD
outputs to the RXD inputs of the PC.

The advantages of this system are great, since no new
communications, software is needed, and the PC can talk and listen
at the same time. In effect, the handshaking is performed by the
intelligence of the RS485 devices attached to the PC.

When wired as in Figure 4-6 below, the PC can transmit
data at any time and all the RS485 devices #1 to #n simultaneously
receives it.

Only one of the RS485 devices may talk, i.e. transmit data,

Chapter 4 Page 47

RS422/485 Information PCI VELOCITY / OPTO ISO RS422/485

at any one time. Each RS485 device recognizes commands and data
addressed to it, it only talks when the PC commands it to do so.
When the RS485 device receives the command to talk from the PC,
it gates its TXD drivers on, sends the data down the device TXD
channel, and disables its TXD drivers. The other RS485 devices
remain in the receive only mode when they are not being addressed,
they do not transmit any data at all. Figure 4-5 gives the jumper
settings for the serial card in the RS485 Full Duplex mode.

Figure 4-5. RS485 Jumpers, Full Duplex.

• Both jumpers left unconnected (not shorted).

Figure 4-6. RS485 Full Duplex.

Note: The receiver end of MAIN line terminated in characteristic

impedance, stubs off the main not terminated.

Chapter 4 Page 48

PCI VELOCITY / OPTO ISO RS422/485 RS422/485 Information

GWG

(

)

Optional Ground ing Arrangements.

Proper operation of the cable circuit, according to TIA EIA:
485 A (1995) requires that the cable ground shield is not connected
directly to the equipment ground shield. A current limiting resistor
should be used in series with the shield to avoid possible large
current flow due to differences in ground potential. Any one of the
methods shown in Figure 4-7, below can do this.

Figure 4-7 - Optional Gr ounding Arra ngements F or A
PCI RS422/485 Card.

Configuration A)

Ω

100

1/2

W

Configuration B)

GWG

SG = Signal Ground Interchange circuit.
GWG = Green wire ground of power system.

= Protective ground of frame ground.

= Circuit ground or circuit

Chapter 4 Page 49

RS422/485 Information PCI VELOCITY / OPTO ISO RS422/485

Configuration A) The circuit common of the equipment is

connected to protective ground, at one point only by a 100
Ω, ±20% resistor with a power dissipation rating of 1/2W. An
additional provision may be made for the resistor to be bypassed
with a strap to connect signal common and protective ground
directly together when specific installation conditions necessitate.

Configuration B) The circuit common shall be connected
directly to protective ground. The same configuration need not be
used at both ends of an interconnection; however, care should be
exercised to prevent establishment of ground loops carrying high
currents. (Note: Under certain ground conditions in configuration
A, above, high ground currents may cause the resistor to fail;
therefore, a provision should be made for inspection and
replacement of the resistor .)

Chapter 4 Page 50

Index PCI VELOCITY / OPTO ISO RS422/485

Index

1 Megabaud......................................................................................................5

115200 Baud...................................................................................................19

16450 / 16550...............................................................................................1, 5

460800 Baud...................................................................................................19

921600 Baud...................................................................................................19

asynchronous....................................................................................................5

Autogating....................................................................................................5, 6

baud / baud rate............................................................................................. 2, 3

BBCARDS.EXE..................................................................................28, 34, 37

Belden............................................................................................................43

bits..................................................................................................................41

buffer..............................................................................................................42

Buffer............................................................................................................. 37

buffer / buffered........................................................................................ 2, 3, 5

cable..................................................................................................3, 13, 40-44

Changing COM numbers in Windows 95.........................................................17

child device.....................................................................................................16

comma n d....................................................................................................2 , 4 6

Configuring Ports In DOS...............................................................................34

Configuring Ports In Microsoft Windows NT. ................................................. 22

Configuring Ports In Windows 3.X..................................................................28

connectors.......................................................................................................12

CTS................................................................................................... 2, 5, 40-43

data word length................................................................................................5

DCD.................................................................................................................2

device driver........................................................................................34, 35, 37

DSR..................................................................................................................2

DTR..................................................................................................................2

emulation.......................................................................................................... 2

fail safe...........................................................................................................41

FIFO............................................................................................................. 1, 5

gating..............................................................................................................43

handsh ake............................................................................................... 1, 2, 41

impeda n ce............................................................................................40-45, 47

instal lation.................................................................................................. 4, 14

Installi ng Ports I n DOS. ..................................................................................34

Installing Ports In Microsoft Windows 95 & 98...............................................14

Installing ports in Windows 3.x.......................................................................29

Installing Ports in Windows NT 4.0.................................................................22

interrupts...........................................................................................................3

Index

PCI VELOCITY / OPTO ISO RS422/485 Index

jumper............................................................................................10, 43, 44-47

last..................................................................................................................45

loop bac k...........................................................................................................3

Maximum Baud Rate ................................................................................18, 19

Megabaud.................................................................................See 921600 baud

mode...........................................................................................................2 , 4 7

open circuit.....................................................................................................41

Optical Isolation.......................................................................5, 7, 9, 16, 28, 34

paren t d evice...................................................................................................16

parity............................................................................................................ 2, 3

party line...................................................................................................41, 45

port / ports ........................................................................... 1, 2, 3, 5, 14, 22, 40

Port Address ...................................................................................................37

protocol ......................................................................................................2, 4 3

receive...........................................................................................11, 45, 46, 47

resistor........................................................................................... 39, 42, 43, 44

RS232..................................................................................................... 1, 5, 10

RS422 / RS485...............................................................5, 6, 8-11, 21, 26, 39-47

RS422 Pinout ..................................................................................................10

RS485 Multiplex Jumper Settings.........................................................10, 21, 26

RTS........................................................................................2, 5, 40-43, 45, 46

RXD............................................................................... 5, 11, 40, 41, 43, 44-46

serial port.................................................................................1, 2, 3, 14, 22, 40

shared interrupt............................................................................................. 3, 4

short circuit.....................................................................................................41

SISR...............................................................................................................35

speed ..........................................................................................................5, 39

technical ...........................................................................................................4

twisted pair.......................................................................................... 11, 40-46

TXD...........................................................................................5, 11, 41, 43-46

Uninstalling Serial Solutions PCI for Windows NT..........................................27

Windows................................................................................................. 1, 3, 22

Index

This Page IntentionallyBlank

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