Black Box IC102C-R2, IC180C User Manual

1000 Park Drive • Lawrence, PA 15055-1018 • [phone] • Fax [phone]

© Copyright 2000. Black Box Corporation. All rights reserved.

CUSTOMER

SUPPORT

INFORMATION

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FREE technical support, 24 hours a day, 7 days a week: Call 724-746-5500 or fax [phone]
Mail order: Black Box Corporation, 1000 Park Drive, Lawrence, PA 15055-1018
Web site: www.blackbox.com • E-mail: [e-mail]

APRIL 2000

IC102C-R2

IC180C

4-Port Serial Host

Adapter with ISP

2

4-PORT CARD SERIAL HOST ADAPTER WITH ISP

3

3

FCC INFORMATION

FEDERAL COMMUNICATIONS COMMISSION

AND

CANADIAN DEPARTMENT OF COMMUNICATIONS

RADIO FREQUENCY INTERFERENCE STATEMENTS

This equipment generates, uses, and can radiate radio frequency energy and if not
installed and used properly, that is, in strict accordance with the manufacturer’s
instructions, may cause interference to radio communication. It has been tested
and found to comply with the limits for a Class A computing device in accordance
with the specifications in Subpart J of Part 15 of FCC rules, which are designed to
provide reasonable protection against such interference when the equipment is
operated in a commercial environment. Operation of this equipment in a
residential area is likely to cause interference, in which case the user at his own
expense will be required to take whatever measures may be necessary to correct the
interference.

Changes or modifications not expressly approved by the party responsible for
compliance could void the user’s authority to operate the equipment.

This digital apparatus does not exceed the Class A limits for radio noise emission from digital
apparatus set out in the Radio Interference Regulation of the Canadian Department of
Communications.

Le présent appareil numérique n’émet pas de bruits radioélectriques dépassant les limites
applicables aux appareils numériques de classe A prescrites dans le Règlement sur le brouillage
radioélectrique publié par le ministère des Communications du Canada.

4

4-PORT CARD SERIAL HOST ADAPTER WITH ISP

NORMAS OFICIALES MEXICANAS (NOM)

ELECTRICAL SAFETY STATEMENT

INSTRUCCIONES DE SEGURIDAD

1. Todas las instrucciones de seguridad y operación deberán ser leídas antes de
que el aparato eléctrico sea operado.

2. Las instrucciones de seguridad y operación deberán ser guardadas para
referencia futura.

3. Todas las advertencias en el aparato eléctrico y en sus instrucciones de
operación deben ser respetadas.

4. Todas las instrucciones de operación y uso deben ser seguidas.

5. El aparato eléctrico no deberá ser usado cerca del agua—por ejemplo, cerca
de la tina de baño, lavabo, sótano mojado o cerca de una alberca, etc..

6. El aparato eléctrico debe ser usado únicamente con carritos o pedestales que
sean recomendados por el fabricante.

7. El parato eléctrico debe ser montado a la pared o al techo sólo como sea
recomendado por el fabricante.

8. Servicio—El usuario no debe intentar dar servicio al equipo eléctrico más allá
a lo descrito en las instrucciones de operación. Todo otro servicio deberá ser
referido a personal de servicio calificado.

9. El aparato eléctrico debe ser situado de tal manera que su posición no
interfiera su uso. La colocación del aparato eléctrico sobre una cama, sofá,
alfombra o superficie similar puede bloquea la ventilación, no se debe colocar
en libreros o gabinetes que impidan el flujo de aire por los orificios de
ventilación.

4

5

10. El equipo eléctrico deber ser situado fuera del alcance de fuentes de calor
como radiadores, registros de calor, estufas u otros aparatos (incluyendo
amplificadores) que producen calor.

11. El aparato eléctrico deberá ser connectado a una fuente de poder sólo del
tipo descrito en el instructivo de operación, o como se indique en el aparato.

12. Precaución debe ser tomada de tal manera que la tierra fisica y la polarización
del equipo no sea eliminada.

13. Los cables de la fuente de poder deben ser guiados de tal manera que no
sean pisados ni pellizcados por objetos colocados sobre o contra ellos,
poniendo particular atención a los contactos y receptáculos donde salen del
aparato.

14. El equio eléctrico debe ser limpiado únicamente de acuerdo a las
recomendaciones del fabricante.

15. En caso de existir, una antena externa deberá ser localizada lejos de las lineas
de energia.

16. El cable de corriente deberá ser desconectado del cuando el equipo no sea
usado por un largo periodo de tiempo.

17. Cuidado debe ser tomado de tal manera que objectos liquidos no sean
derramados sobre la cubierta u orificios de ventilación.

18. Servicio por personal calificado deberá ser provisto cuando:
A: El cable de poder o el contacto ha sido dañado; u

B: Objectos han caído o líquido ha sido derramado dentro del aparato; o
C: El aparato ha sido expuesto a la lluvia; o
D: El aparato parece no operar normalmente o muestra un cambio en su

desempeño; o

E: El aparato ha sido tirado o su cubierta ha sido dañada.

5

NOM STATEMENT

6

4-PORT CARD SERIAL HOST ADAPTER WITH ISP

EMC Directive Statement

Products bearing the CE label fulfill the requirements of the EMC directive
(89/336/EEC) and of the low-voltage directive (73/23/EEC) issued by the
European Commission.

To obey these directives, these European standards must be met:

• EN55022 Class A — “Limits and methods of measurement of radio
interference characteristics of information technology equipment.”

• EN50082-1 — “Electromagnetic compatibility — Generic immunity standard”
Part 1: Residential, commercial, and light industry.

• EN60950 (IEC950) — “Safety of information technology equipment, including
electrical business equipment.”

Trademarks Used in this Manual

IBM, OS/2, PAL, and PS/2 are registered trademarks of International Business
Machines Corporation.

Windows NT is a trademark, and Windows is a registered trademark, of Microsoft
Corporation.

UL is a registered trademark of Underwriters Laboratories Incorporated.
Any other trademarks mentioned in this manual are acknowledged to be the

property of the trademark owners.

WARNING

Always use the cabling provided with this product if possible. If no
cable is provided or if an alternate cable is required, use high-quality
shielded cabling to maintain compliance with FCC/EMC directives.

7

CONTENTS

Contents

Chapter Page

1. Specifications...........................................................................................................8

2. Introduction ............................................................................................................9

2.1 Overview............................................................................................................9

2.2 Technical Description....................................................................................10

2.2.1 Interrupt Status Port (ISP)..................................................................10

2.2.2 Connector Pin Assignments................................................................11

3. Configuration ........................................................................................................13

3.1 Address Selection............................................................................................13

3.2 Jumper Selections ..........................................................................................15

3.3 IRQ Selection..................................................................................................15

3.4 Interrupt Modes..............................................................................................16

3.5 Clock Modes....................................................................................................17

3.6 Baud Rates and Divisors for the “DIV1” Mode ............................................19

3.7 Baud Rates and Divisors for the “DIV2” Mode ............................................20

4. Installation .............................................................................................................21

4.1 Installing the Adapter in Your Operating System.........................................21

4.1.1 Windows 3.1x..........................................................................................21

4.1.2 Windows 95/98.......................................................................................21

4.1.3 Windows NT ...........................................................................................21

4.2 Installing the Hardware..................................................................................21

5. Troubleshooting....................................................................................................23

Appendix A: The RS-232 Interface............................................................................24

Appendix B: Asynchronous Communications..........................................................25

Appendix C: Circuit-Board Diagram ........................................................................27

8

4-PORT CARD SERIAL HOST ADAPTER WITH ISP

Maximum Data Rate — IC102C-R2: Up to 460.8 Kbps;

IC180C: 460.8 kbps and higher

Maximum Data Distance — Up to 50 feet (15.2 m)
Number of Ports — (4) RS-232
Connectors — DB37 to (4) DB25 male
Communications Chip — IC102C-R2: 16554 UART; IC180C: 16950 UART
Manufacturing — IPC 610-A Class-III standards are adhered to

with a 0.1 visual A.Q.L. and 100% functional
testing. This circuit board is built to UL

®

94V0
rating and is 100% electrically tested. This
printed circuit board is solder mask over bare
copper or solder mask over tin nickel.

Operating Temperature — 32 to 122°F (0 to 50°C)
Storage Temperature — -4 to +158°F (-20 to +70°C)
Humidity Range — 10 to 90% relative humidity, non-condensing
MTBF — Greater than 150,000 hours
Power — +5V @ 210 mA, ±12V @ 80 mA each
Size — 3.4"H x 5.2"L (8.6 x 13.2 cm)
Cable Length — 36 inches (91.4 cm)

8

1. Specifications

9

CHAPTER 2: Introduction

2.1 Overview

The 4-Port Card Serial Host Adapter with ISP provides the PC with four RS-232
asynchronous ports. This Adapter allows for connection to any device (such as
modems, data-entry terminals, and plotters) using the RS-232 electrical interface.

The Adapter is shipped with the items listed below. If any of these items are
missing or damaged, call Black Box.

• The 4-Port Card Serial Host Adapter with ISP,

• a DB37 to (4) DB25 spider cable (an optional DB9 spider cable is available;
call Technical Support for details),

• (2) 3.5" serial utility diskettes, and

• this user’s manual.

The Adapter’s factory-default settings are:

Port # Base Address IRQ IRQ Mode Clock Divisor

Port 1 280 5 M 4
Port 2 288 5 S 4
Port 3 290 5 S 4
Port 4 298 5 S 4

To install the 4-Port Card Serial Host Adapter with ISP using factory-default
settings, refer to Chapter 4.

For your reference, record your installed Adapter settings below.

Port # Base Address IRQ IRQ Mode Clock Divisor

Port 1
Port 2
Port 3
Port 4

2. Introduction

10

4-PORT CARD SERIAL HOST ADAPTER WITH ISP

2.2 Technical Description

The IC102C-R2 Adapter uses the 16554 UART. This chip features programmable
baud rate, data format, interrupt control, and a 16-byte input and output FIFO,
and is functionally 4 16550 UARTs. The IC180C uses 16950 UARTs, which feature
a 128-byte FIFO.

This Adapter features:

• Sharable IRQs that allow more than one port to share a single IRQ.

• Support for IRQs 3–7, 9–12, and 15.

• 16554 buffered Quad UART (IC102C-R2) or 16950 UART (IC180C).

• Easier integration with 16-bit address decode.

• Speeds up to 460.8 Kbps.

• Multiple clocking modes that ensure compatibility with existing software
products.

2.2.1 I

NTERRUPTSTATUSPORT

(ISP)

The 4-Port Card Serial Host Adapter with ISP provides you with an Interrupt Status
Port (ISP) for greater throughput when servicing multiple ports on a single
interrupt line. The ISP is a read-only 8-bit register that sets a corresponding bit
when an interrupt is pending. Port 1 interrupt line corresponds with Bit D0 of the
status port, Port 2 with D1, etc.

The ISP is located at Base+7 on each port. (For example, Base = 280 Hex, Status
Port = 287.) This allows any one of eight locations to be read to obtain the value in
the status register. All four status ports on the Adapter are identical, so any one of
the four can be read to determine which interrupt is pending. In the example
below, Channel 2 has an interrupt pending.

Bit Position: 7 6 5 4 3 2 1 0
Value Read: 0 0 0 0 0 0 1 0

11

CHAPTER 2: Introduction

2.2.2 C

ONNECTORPINASSIGNMENTS

DB25 (RS-232 DTE)

Signal Name Pin # Mode

GND Ground 7
TD Transmit Data 2 Output
RTS Request To Send 4 Output
DTR Data Terminal Ready 20 Output
RD Receive Data 3 Input
CTS Clear To Send 5 Input
DSR Data Set Ready 6 Input
DCD Data Carrier Detect 8 Input
RI Ring Indicator 22 Input

DB9 (EIA-574 DTE)

Signal Name Pin # Mode

GND Ground 5
TD Transmit Data 3 Output
RTS Request To Send 7 Output
DTR Data Terminal Ready 4 Output
RD Receive Data 2 Input
CTS Clear To Send 8 Input
DSR Data Set Ready 6 Input
DCD Data Carrier Detect 1 Input
RI Ring Indicator 9 Input

12

4-PORT CARD SERIAL HOST ADAPTER WITH ISP

DB37

Port # 1 2 3 4

GND 33 14 24 5
TD 35 12 26 3
RTS 17 30 8 21
DTR 34 13 25 4
RD 36 11 27 2
CTS 16 31 7 22
DSR 18 29 9 20
DCD 37 10 28 1
RI 15 32 6 23

13

CHAPTER 3: Configuration

The 4-Port Card Serial Host Adapter with ISP contains several jumper straps that
must be set for proper operation.

3.1 Address Selection

Each port on the 4-Port Card Serial Host Adapter with ISP occupies eight
consecutive I/O locations. A DIP switch is used to set the base address for these
locations.

The Adapter has a unique addressing scheme that provides the ability to select
specific non-linear address combinations (for example, 3F8, 2F8, 3E8, 2E8).

One way to select port addresses is to choose them from the table of available
address combinations below. If different address combinations are required,
contact Technical Support about custom PAL

®

options.

Table 3-1. Available address combinations

Switch 6 Switch 7 Switch 8 Port 1 Port 2 Port 3 Port 4

On On Off 3F8 2F8 3E8 2E8
On Off On 2F8 3E8 2E8 2E0
On Off Off 3E8 2E8 280 288
Off On On 500 508 510 518
Off On Off 580 588 590 598
Off Off On 1500 1508 1510 1518
Off Off Off 3220 3228 4220 4228
On On On Addresses set up by switches 1–5.

NOTE

Each COM: port in the system should have a unique address. Typically
COM1:–COM4: addresses are 3F8, 2F8, 3E8, and 2E8 Hex. Refer to
Chapter 5 for common address contentions.

3. Configuration

14

4-PORT CARD SERIAL HOST ADAPTER WITH ISP

There’s also a second mode of address selection. In this mode, the DIP switch sets
the base address and the Adapter occupies 32 consecutive I/O locations. The table
below illustrates the location of each port and its relationship to the other ports.

NOTE

For switches 1–5 to become active, switches 6, 7, and 8 must be set in
the “On” (Up) position.

Table 3-2. Address selection

Switch Settings

Address Lines→ A9 A8 A7 A6 A5

Address Selected 1 2 3 4 5

280-29F Off On Off On On
2A0-2BF Off On Off On Off
380-39F Off Off Off On On
1A0-1BF On Off Off On Off
2E0-2FF Off On Off Off Off

The illustration below shows the correlation between the DIP-switch setting and
the address bits used to determine the base address. In the example below, the
address 2E0 is selected as a base. Address 2E0 in binary is XX 10 111X XXXX,
where X = a non-selectable address bit.

Figure 3-1. DIP-switch settings.

A9

A5

ON

OFF

1 2 3 4 5 6 7 8

15

CHAPTER 3: Configuration

Table 3-3. Port to connector

Port # Connector Location Address Example (Base=2E0)

1 1 Base+0 2E0-2E7
2 2 Base+8 2E8-2EF
3 3 Base+16 2F0-2F7
4 4 Base+24 2F8-2FF

3.2 Jumper Selections

For ease of configuration, the headers are grouped by port. Port 1 headers have a
“J1” prefix, Port 2 headers have the “J2” prefix, etc. For example, the header that
controls the Port 1 IRQ selection is J1B, the header that controls the Port 2 IRQ
selection is J2B. The silk-screen also provides information for configuring the
Adapter without the use of the manual. This is particularly useful in field re­configuration.

3.3 IRQ Selection

Headers J1B through J4B select the interrupt request for each serial port. If COM1:
is selected, the corresponding jumper must be on the IRQ4 setting. If COM2: is
selected, the corresponding jumper must be on IRQ3. (This only applies to the
traditional DOS COM port assignments; in Windows

®

COM1: can use I/O address

300 and IRQ15 if it is available).

Figure 3-2. Headers J1B-J4B, IRQ selection.

3 4 5 6 7 9 10 11 12 15

16

4-PORT CARD SERIAL HOST ADAPTER WITH ISP

NOTE

Most DOS communications software applications default COM3: to IRQ4
and COM4: to IRQ3. This requires the sharing of interrupts between
COM1: and COM3:, and between COM2: and COM4:. While this is the
default, it is not always the best setting. Check your software
configuration instructions to determine the most appropriate IRQ
selection.

Any two or more ports can share a common IRQ by placing the jumpers on the
same IRQ setting and setting the appropriate selections at J1A through J4A. When
sharing IRQs, many operating systems (for example, Windows NT

™

) will require
the location of the Interrupt Status Port (ISP). See Section 2.2 for a description of
the ISP and how it is used.

3.4 Interrupt Modes

Headers J1A through J4A select the interrupt modes for each port. Each port must
be set in the correct mode to ensure proper operation.

“N” indicates the normal, single interrupt per port mode. “S” indicates the shared
interrupt mode, which allows more than one port to access a single IRQ. “M”
indicates that a 1K-ohm pull-down resistor is required on one port when sharing
interrupts.

Figure 3-3. Header J1A, normal IRQ mode.

J1A

N S M

17

CHAPTER 3: Configuration

Set the jumpers to “S” for shared interrupt mode on all blocks sharing an IRQ
except one. Set that port block for “M.” This provides the pull-down resistor circuit
that makes sharing IRQs possible. If you are using more than one 4-Port Card
Serial Host Adapter with ISP or a compatible adapter in a bus, you should only
have one port set to “M.” The following example shows two ports sharing a single
IRQ.

Figure 3-4. Header J1A and J2A, shared IRQ mode.

Set the jumper to “S” if you are using more than one 4-Port Card Serial Host
Adapter with ISP in a bus or to completely remove the pull-down resistor for
hardware compatibility. Setting the adapter in this configuration when it is not

accompanied by a pull-down resistor will prevent the ports from triggering an interrupt.

3.5 Clock Modes

You can select from “divide by 4,” “divide by 2,” and “divide by 1” clocking modes.
This mode is selected at J5.

J1A

N S M

J2A

N S M

18

4-PORT CARD SERIAL HOST ADAPTER WITH ISP

To select the baud rates commonly associated with COM ports (for example, 2400,
4800, 9600, 19.2,...115.2 Kbps) place the jumper in the divide by 4 mode (silk­screened DIV4).

Figure 3-5. Clocking mode “Divide By 4.”

To double these rates up to a maximum rate of 230.4 Kbps, place the jumper in
the divide by 2 (silk-screened DIV2) position.

Figure 3-6. Clocking mode “Divide By 2.”

To select the maximum data rate (460.8 Kbps), place the jumper in the divide by 1
(silk-screened DIV1) position.

Figure 3-7. Clocking mode “Divide By 1.”

DIV1
DIV2
DIV4

DIV1
DIV2
DIV4

DIV1
DIV2
DIV4

19

CHAPTER 3: Configuration

3.6 Baud Rates and Divisors for the “DIV1” Mode

The following table shows some common data rates and the rate you should
choose to match them if using the Adapter in the DIV1 mode.

For this data rate... choose this data rate

1200 bps 300 bps
2400 bps 600 bps
4800 bps 1200 bps
9600 bps 2400 bps

19.2 Kbps 4800 bps

57.6 Kbps 9600 bps

115.2 Kbps 19.2 Kbps

230.4 Kbps 57.6 Kbps

460.8 Kbps 115.2 Kbps

If your communications package allows the use of baud rate divisors, choose the
appropriate divisor from this table:

For this data rate... choose this data rate

1200 bps 384
2400 bps 192
4800 bps 96
9600 bps 48

19.2 Kbps 24

38.4 Kbps 12

57.6 Kbps 8

115.2 Kbps 4

230.4 Kbps 2

460.8 Kbps 1

20

4-PORT CARD SERIAL HOST ADAPTER WITH ISP

3.7 Baud Rates and Divisors for the “DIV2” Mode

The following table shows some common data rates and the rate you should
choose to match them if using the Adapter in the DIV2 mode.

For this data rate... choose this data rate

1200 bps 600 bps
2400 bps 1200 bps
4800 bps 2400 bps
9600 bps 4800 bps

19.2 Kbps 9600 bps

38.4 Kbps 19.2 Kbps

57.6 Kbps 38.4 Kbps

115.2 Kbps 57.6 Kbps

230.4 Kbps 115.2 Kbps

If your communications package allows the use of baud-rate divisors, choose the
appropriate divisor from this table:

For this data rate... choose this divisor

1200 bps 192
2400 bps 96
4800 bps 48
9600 bps 24

19.2 Kbps 12

38.4 Kbps 8

57.6 Kbps 4

115.2 Kbps 2

230.4 Kbps 1

21

CHAPTER 4: Installation

The 4-Port Card Serial Host Adapter with ISP can be installed in any of the PC
expansion slots. The Adapter contains several jumper straps for each port that
must be set for proper operation—see Chapter 3.

IMPORTANT

You MUST set up the operating system BEFORE you physically install
the Card.

4.1 Installing the Adapter in Your Operating System

If you are installing an ISA adapter in DOS, OS/2, or QNX, please refer to
the appropriate directory on the Serial Utilities Disk for instructions.

4.1.1 W

INDOWS

3.1

X

Please refer to the /WINDOWS sub-directory on the Serial Utilities Diskette for
help files and current information on the installation of the Card in this operating
environment.

4.1.2 W

INDOWS

95/98 U

SERS

For the ISA card, run setup on the Serial Utilities Diskette before installing
the card. Make note of the resources that Windows assigns the adapter and
set the adapter to match those resources. Power down the computer and
install the adapter.

4.1.3 W

INDOWS

NT

For the ISA card, run setup on disk two of the Serial Utilities Diskettes
before installing the card. After installing the software, refer to the help file
that automatically comes up for installation instructions.

Installation is complete.

4.2 Installing the Hardware

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. Installation

22

4-PORT CARD SERIAL HOST ADAPTER WITH ISP

4. Gently insert the Adapter into the slot. Make sure that the Adapter is seated
properly.

5. For the IC102C-R2 or IC180C connect the DB37 female connector end of the

octopus cable to the DB37 male connector on the card.

6. Replace the screw.

7. Replace the cover.

8. Install the spider cable.

9. Connect the power cord.

If you wish to change any resources assigned to the adapter, refer to the
help file installed in the Black Box folder in the Start, Programs menu.

23

CHAPTER 5: Troubleshooting

A Serial Utility Diskette is supplied with the Adapter and will be used in the
troubleshooting procedures. By using this diskette and following these simple
steps, most common problems can be eliminated 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 the 4-Port Card Serial Host Adapter with ISP so that there is no
conflict with currently installed adapters. No two adapters can occupy the same
I/O address.

3. Make sure the Adapter is using a unique IRQ. While the 4-Port Card Serial
Host Adapter with ISP does allow the sharing of IRQs, many other adapters,
such as SCSI adapters and on-board serial ports, do not. The IRQ is typically
selected via an on-board header block. Refer to Chapter 3 for help in choosing
an I/O address and IRQ.

4. Make sure the Adapter is securely installed in a motherboard slot.

5. Use the supplied diskette and this manual to verify that the Adapter is
configured correctly. The supplied diskette contains a diagnostic program
(“SSD”) that will verify if the Adapter is configured properly. Refer to the
“README” file on the diskette for detailed instructions on using “SSD.”

6. Refer to the diskette for any postproduction manual updates and application­specific information.

7. Always use this diagnostic software when troubleshooting a problem. This will
eliminate the software issue from the equation.

5. Troubleshooting

24

4-PORT CARD SERIAL HOST ADAPTER WITH ISP

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-C/D/E or EIA/TIA-232-C/D/E. It is defined as “Interface between Data

Terminal Equipment and Data Circuit-Terminating Equipment Employing Serial Binary
Data Interchange.”

The mechanical implementation of RS-232 is on a DB25 connector. The IBM

®

PC
computer defined the RS-232 port on a DB9 connector and subsequently the
EIA/TIA approved this implementation as the EIA/TIA-574 standard. This
standard has been defined as the “9-Position Non-Synchronous Interface between Data

Terminal Equipment and Data Circuit-Terminating Equipment Employing Serial Binary
Data Interchange.” Both implementations are in widespread use and are referred to

as RS-232 in this document.
RS-232 is capable of operating at data rates up to 20 Kbps/50 ft. (15.2 m). The

absolute maximum data rate may vary with line conditions and cable lengths. RS­232 often operates at 38.4 Kbps or more over very short distances.

The voltage levels defined by RS-232 range from -12 to +12 volts. RS-232 is a single­ended 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 (-3 to -10
volts) represents a binary 1 (mark).

The RS-232 and the EIA/TIA-574 specification define two types of interface
circuits: Data Terminal Equipment (DTE) and Data Circuit-Terminating (DCE).
This adapter is a DTE interface.

Appendix A. The RS-232 Interface

25

APPENDIX B: Asynchronous Communications

Serial data communications implies that individual bits of a character are
transmitted consecutively to a receiver that assembles the bits back into a character.
Data rate, error checking, handshaking, and character framing (start/stop bits) are
pre-defined and must correspond at both the transmitting and receiving ends.

Asynchronous communications is the standard means of serial data
communication for PC compatibles and PS/2

®

computers. The original PC was
equipped with a communication or COM port that was designed around an 8250
Universal Asynchronous Receiver/Transmitter (UART). This device allows
asynchronous serial data to be transferred through a simple and straightforward
programming interface. A starting bit followed by a pre-defined number of data
bits (5, 6, 7, or 8) defines character boundaries for asynchronous communications.
The end of the character is defined by the transmission of a pre-defined number of
stop bits (usual 1, 1.5, or 2).

Figure B-1. Asynchronous communications bit.

Appendix B. Asynchronous

Communications

Idle State

of

Line

1

5 to 8 Data Bits

Even

or

Unused

Parity

Bit

Remain Idle

or

Next Start Bit

Odd

0

1

1.5
2

Stop Bits

26

4-PORT CARD SERIAL HOST ADAPTER WITH ISP

An extra bit used for error detection is often appended before the stop bits. This
special bit is called the parity bit. Parity is a simple method of determining if a data
bit has been lost or corrupted during transmission. There are several methods for
implementing a parity check to guard against data corruption. Common methods
are called (E)ven Parity or (O)dd Parity. Sometimes parity is not used to detect
errors on the data stream. This is referred to as (N)o parity.

Because each bit in asynchronous communications is sent consecutively, it is easy
to generalize asynchronous communications by stating that each character is
wrapped (framed) by pre-defined bits to mark the beginning and end of the serial
transmission of the character. The data rate and communication parameters for
asynchronous communications have to be the same at both the transmitting and
receiving ends. The communication parameters are baud rate, parity, number of
data bits per character, and stop bits (for example, 9600, N, 8, 1).

27

APPENDIX C: Circuit-Board Diagram

Appendix C. Circuit-Board

Diagram

3.10 in.

P3

C5

5.20 in.

U3

C2

Y1

COPYRIGHT 1997

C10

GD75232

C7

U5

E2

E1

D1

+

MADE IN USA

C1

J1A

R1

N S M

GD75232

U6

74LS74

U1

3 4 5 6 7 9 10 11 12 15

J1B

C8

D2

J2A

C3

DIV1

R2

N S M

J2B

3.40 in.

GD75232

U7

R7

16C554

RP1

R5

DIV2

DIV4

J5

D3

3 4 5 6 7 9 10 11 12 15

J3A

C11

C9

SW1

SWITCH8DIP

R3

N S M

J3B

GD75232

U8

S1
S2
S3
A5
A6
A7
A8
A9

D4

3 4 5 6 7 9 10 11 12 15

J4A

C12

C6

R6

R4

N S M

74LS245

74LS244

XC9536-3405

U2

3 4 5 6 7 9 10 11 12 15

J4B

P1

U9

U4

C4

P2