User's Manual

Table Of Contents

OSMAC Base User Manual

Page 37

Manu.01_0405

The OSMAC Base is wired as a peripheral (DCE) device.

The control lines on the serial port are used for controlling the flow of data and the peripheral attached

to the port. The most signals provided for on RS-232 serial interfaces are shown in the following table:

Pin # Name Typical RS-232 Serial Signal Functions

3TXD

Transmit data from the computer to the OSMAC Base.

2RXD

Receive Data from the OSMAC Base to the computer.

7 RTS* Request to send data. This is an output from the computer to the

OSMAC Base. It indicates to the OSMAC Base that it is ready to

exchange data.

8CTS*

Clear to send. This is a signal from the OSMAC Base to the

computer indicating that it is OK to send data.

4DTR*

Data Terminal Ready to the OSMAC Base. This signal indicates

to the peripheral that the host is ready to receive data.

1 DCD*

Data Carrier Detect from the OSMAC Base.

9 RI* Not implemented.

6 DSR Data Set Ready from the peripheral. Indicates the peripheral is

ready.

5 GND System Ground

*The hardware flow control signals, RTS, CTS, DTR, DSR, and DCD are active low. In other words,

they are set to binary zero (0) to assert them and binary one (1) to negate them. Over an RS-232

cable, they are again inverted because RS-232 specification calls for negative logic. Negating RTS is a

binary 1, which is a negative voltage on the RS-232 port.

10.4 Auxiliary/Alarm Connector

A 15 pin D-Sub female connector is located on the rear of the unit. This connector has digital inputs

used for triggering alarms. It also has contacts for two relay outputs. The digital inputs may be

programmed to automatically generate a page or dial the phone. The relay outputs may be switched

on remotely via the telephone, radio, or console.

Note that all digital alarm inputs have an internal 10K pull-up resistors connected. Alarms are

activated by pulling the input to ground. Open circuit or a TTL/CMOS high level is the inactive state.

Do not pull these inputs above 5V.

Auxiliary/Alarm I/O Connector Pin Out

Pin Number Function

Alarm 8