Owner`s manual

9
Serial ports on the MOD 24-4CF I/O module have DB-25 female DCE
ports. DCE ports use the following signals for communication:
DCE PORT PIN/SIGNAL DEFINITION
Pin Signal
(EIA-232)
Directio
n
Description
1 PGND --- Protective Ground
2 Tx Input Data In
3 Rx Output Data Out
4 RTS Input Internally Enabled if No Wire Connected (Normally Not Used)
5 CTS Output -12V When Buffer is Full
6 DSR Output +12V When Model 24H Powers Up
7 SGND --- Signal Ground
8 DCD Output +12V When Model 24 Powers Up
20 DTR Input Transmit Enabled When +12V
If you are interfacing a DCE device to the Model 24H (DTE), you must
use a one-to-one or straight cable as shown in Figure 2 . If you are
interfacing a DTE device to the Model 24H (DTE), you must use a
crossed cable as shown in Figure 3 .
When using XON/XOFF protocol, it may be desirable to use cables with
only Tx, Rx and GND (Signal Ground) connected. On the serial ports
of a BayTech Model 24H, input handshaking lines are enabled if
nothing is connected, allowing the system to operate with only Tx, Rx
and GND connected.
CAUTION: Do not attempt to use a serial cable on a parallel port.
Since an EIA-232 serial port usually carries a potential of +12 and -12
volts, plugging a serial cable from that port into a parallel port may
cause damage to the parallel port.