21 APPENDIX

COM CONNECTOR

All descriptions in the PC CONTROL COMMAND TABLE are for the users convenience only. KENWOOD will not support or warrantee this documentation in any way.

HARDWARE DESCRIPTION

This transceiver uses a full-duplex, asynchronous, serial interface for communicating through the male 9-PIN RS-232C COM connector. Each data is constructed with 1 start bit, 8 data bits, and 1 stop bit (4800 bps must be configured as 2 stop bits). No parity is used. The pinout and the pin functions of the COM connector are shown below:

COM

 

9

8

7

 

6

 

 

5

4

3

2

1

 

 

Rear panel view

 

COM

COM Pin Name

 

 

 

Function

I/O

Pin No. (Ref.: Computer)

 

(Ref.: Transceiver)

 

 

1

NC

 

 

 

—

—

2

RXD

 

 

Transmit data

Output

3

TXD

 

 

Receive data

Input

4

NC

 

 

 

—

—

5

GND

 

Signal ground

 

6

NC

 

 

 

—

—

7

RTS

 

Receive enable

Input

8

CTS

 

Transmit enable

Output

9

NC

 

 

 

—

—

RXD: Transmit data is serial data transferred from the transceiver to the computer.

TXD: Receive data is serial data transferred from the computer to the transceiver.

GND: Signal ground pin

RTS: This signal is applied to the transceiver. It is used to inhibit transmit data from the transceiver when the computer is not ready to receive data. Transmit data is inhibited when the level is low.

CTS: This signal is applied from the transceiver. It is used to inhibit transmit data from the computer when the transceiver is not ready to receive data. Transmit data is stopped when the level is low.

CONTROL OPERATION

Most computers handle data in the form of “bits” and “bytes”. A bit is the smallest piece of information that a computer can handle. A byte is composed of eight bits. This is the most convenient form for most computer data. This data may be sent in the form of either serial or parallel data strings. The parallel method is faster but more complicated, while the serial method is slower and requires less complicated equipment. The serial form is, therefore, a less expensive alternative.

Serial data transmission uses time-division methods over a single line. Using a single line also offers the advantage of reducing the number of errors due to line noise.

Only 3 lines are required theoretically for control of the transceiver via the computer:

•Transmit data

•Receive data

•Ground

From a practical standpoint, it is also necessary to incorporate some means of controlling when this data transfer will occur. The computer and transceiver cannot be allowed to send data at the same time! The required control is achieved by using the RTS and CTS lines.

For example, the transceiver is placed into the transmit mode whenever the character string “TX;” is sent from the computer. The character string “TX;” is called a computer control command. It tells the transceiver what to do. There are numerous commands available for control of the transceiver. These commands may be incorporated into a computer program written in any high level language. Programming methods vary from computer to computer; therefore, refer to the instruction manuals provided with the terminal program and computer.

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