Comtech EF Data CDM-550T - Manual (Page 93)

Chapter 9. RS-232 DATA
INTERFACE - ASYNCHRONOUS
OPERATION
9.1 Introduction
The CDM-550T supports asynchronous RS-232 in addition to synchronous RS-232 formats. This
is useful, for example, in connecting two computers together, via their serial ports, at opposite
ends of a satellite link. There are, however, some restrictions and limitations when using this
mode and the user may have to experiment a little in order to get reliable communication.
9.2 ASYNC EIA-232 Specifications
Maximum operating baud rate:
57.6 kbaud (QPSK and OQPSK)
28.8 kbaud (BPSK)
Additional data overhead required:
Zero. A 9.6 kbaud connection uses a 9.6 kbps
carrier.
Maximum allowable baud rate tolerance: ± 600 ppm
Character formats supported:
Any, except those using 1.5 stop bits (see note
below)
Flow control: None
Handshaking line supported: Data Carrier Detect (DCD)
Connectivity required: Rx data, Tx Data and Ground (DCD optional)
9.3 Setup
The setup required for this mode is remarkably simple. Select RS-232 as the interface type, and
then select the required baud rate for both transmit and receive data rates. Detection of the
asynchronous mode is fully automatic. If no clock is detected, asynchronous mode is assumed,
and the internal circuitry is switched accordingly. The settings for both Tx and Rx clocking are
9–1