Allen-Bradley A-B QUALITY DL20 Series User Manual page 71

Chapter 6
The Serial Port
Slave Mode
6–6
When DL20s are connected on an RS-422 network, the port must be set as an
input using the Set Up Master special function. Since DL10 slaves are
addressed using the RS-422 port as an output, using DL20s as addressable
masters precludes the use of this port for sending data out to DL10 slaves.
Entering Slave Mode
Enable the slave mode by sending the DL20 the following control sequence,
while in the run mode:
[CTRL D] [Address] [Return]
Exiting Slave Mode
While in the slave mode, the DL20 will not respond to message number
triggers. To exit the slave mode, send the following control sequence:
[CTRL S] [Address] [Return]
Note: If the DL20 is powered down in the slave mode, it will power up in
the normal run mode, not slave mode.
Slave Mode Protocol
Slave mode protocol is as follows.
20 DISPLAY
CHARACTERS ADDRESS
1. Send the 20 display characters. Any valid ASCII character, upper or
lowercase, can be sent. Previously described control codes do not apply.
2. Send the address. This is a one-byte character, ranging anywhere from 1
through 127 decimal (1 through 7F hex). If the address is 65, type the
character "A".
Note: Restrictions for address byte are the same as described previously
for the addressable master feature. Any packet containing the address
127 is received by all DL20s, regardless of their address.
3. Send the line number. Valid line numbers are line 1 through line 4. Send
the decimal equivalent values not the ASCII value:
Line 1 = CTRLA
Line 2 = CTRLB
Line 3 = CTRLC
Line 4 = CTRLD
4. Send the carriage return [Return].
Slave Mode Control Codes
There are certain control codes that slave DL20s respond to:
SLAVE LINE
NUMBER
CARRIAGE
RETURN