Allen-Bradley MicroLogix 1200 Reference Manual page 404

E-12 Protocol Configuration
Table E.8 Modbus RTU Slave Communications Configuration Parameters
(MicroLogix 1200 Controllers and MicroLogix 1500 Series B and higher Processors only)
Parameter Options
Baud Rate 300, 600, 1200, 2400, 4800, 9600, 19.2K, 38.4K
Parity none, even, odd
Node Address 1 to 247 decimal
Control Line no handshaking, Half-Duplex modem
Inter-character 0 to 6553 (can be set in 1 ms increments); 0 = 3.5 character times
Timeout (x1 ms)
Specifies the minimum delay between characters that indicates the end of a message packet.
Modbus Data Table Coils (Discrete outputs, Modbus addresses 0001 to 4096) range = 3 to 255, 0 = no file
File Number
Contacts (Discrete inputs, Modbus addresses 10001 to 14096) range = 3 to 255, 0 = no file
Assignment
Input Registers (Read Only, Modbus addresses 30001 to 30256) range = 3 to 255, 0 = no file
Holding Registers (Read/Write, Modbus addresses 40001 to 40256) range = 3 to 255, 0 = no
file
RTS Off Delay 0 to 65535 (can be set in 20 ms increments)
(x20 ms)
Specifies the delay time between when the last serial character is sent to the modem and
when RTS is deactivated. Gives the modem extra time to transmit the last character of a
packet.
RTS Send Delay 0 to 65535 (can be set in 20 ms increments)
(x20 ms)
Specifies the time delay between setting RTS until checking for the CTS response. For use
with modems that are not ready to respond with CTS immediately upon receipt of RTS.
Pre Transmit Delay 0 to 65535 (can be set in 1 ms increments)
(x1 ms)
When the Control Line is set to no handshaking, this is the delay time before transmission.
Required for 1761-NET-AIC physical Half-Duplex networks. The 1761-NET-AIC needs delay
time to change from transmit to receive mode.
When the Control Line is set to Half-Duplex Modem, this is the minimum time delay between
receiving the last character of a packet and the RTS assertion.
Publication 1762-RM001C-EN-P
When the system driver is Modbus RTU Slave, the following
communication port parameters can be changed:
Programming
Software Default
19.2K
none
1
no handshaking
0
0
0
0
0
0
0
0