Allen-Bradley A-B QUALITY DL20 Series User Manual page 67

Chapter 6
The Serial Port
Serial Data Format
Using the Serial Port
6–2
The format is the same for both the RS-232 and RS-422 ports. The device
connected to either serial port must match the DL20. The transmission
standards used by the DL20 are:
Baud Rate:
Data Length:
Parity:
Stop Bits:
Note: Literature for non Allen-Bradley terminals may be misleading.
Setting eight data bits and selecting parity sometimes results in nine total
data bits. Only eight bits should be sent. Also, the DL20 accepts data sent
with 1-1/2 or 2 stop bits.
Note that both the serial port and the parallel port cannot be used
simultaneously. One or the other must be chosen to input data.
Chapter 7, describes the parallel port. Refer to Chapter 9 for serial port
connections.
Selecting Serial Port Parameters
Serial port parameters, such as baud rate and parity, are set using the special
function Set Up I/O Ports. Chapter 8 describes the serial port setup
procedures.
Serial Data Format
The DL20 must be set for BINARY MSG & VAR DATA of the parallel port
options if the serial port is used to input data and message triggers. This is
true even though the parallel port is not being used. The Set-Up I/O Port
special function (explained in Chapter 8) sets the DL20 up for binary data
input. This restriction is due to the internal operation of the DL20.
Host messages to the serial port contain three fields:
CONTROL
CODE
300, 1200, or 9600
8 Bits (including parity if any)
Odd, Even, None
1
CARRIAGE
DIGITS
RETURN