User`s manual

99
FX3U Series Programmable Controllers
User’s Manual - MODBUS Serial Communication Edition
10 Creating Programs
10.4 Cautions on Program Creation
1
Outline
2
Specifications
3
System Configuration
4
Wiring
5
Communication Setup
6
Related Devices and Comm. Status
7
MODBUS Standard Commands
8
Master Specification
9
Slave Specification
10
Creating Programs
10.4 Cautions on Program Creation
1. MODBUS Configuration Request Flag (M8411)
When setting up FX MODBUS Serial Communication on either Channel 1 or 2, be sure to use Special
Auxiliary Relay M8411 as shown in Chapter 5 of this manual.
2. Using the ADPRW Command
1) When using the ADPRW command in the FX MODBUS Master, make sure the driving contact of the
ADPRW command stays ON until the command has been completed (M8029).
2) When driving multiple ADPRW commands at the same time in the FX MODBUS Master, only one
command will be executed at a time. The next ADPRW command in the program is executed after the
current command has been completed.
3. Reading Coils
When using the Read Coils command (Command Code 0x01) in the FX MODBUS Master with a word device
(i.e. D, or R) as the destination device, only the number of bits assigned in the device count of the ADPRW
command will be overwritten. The remaining bits of the word device will not be affected.