User`s manual
33
FX3U Series Programmable Controllers
User’s Manual - MODBUS Serial Communication Edition
6 Related Devices and Communication Status
6.1 Special Data Registers
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
D8405 D8425
Communication
Format
Display
M, S This device stores the communication format set in the PLC. R
D8406 D8426
ASCII Input
Delimiter
M, S
Displays the End Of Message character used in ASCII mode.
By default this is the LF (0x0A) character.
Special clear conditions:
1) Power on
Note: In the Master this character can be changed by the user
program. For the slave this is a read only device. Refer
to the Change Ascii Input Delimiter command in the
section 8.2.
R,W
D8407 D8427
Step Number
Being Executed
M
Last step number of the MODBUS command that was
executed (0 if no command is executed in the program).
After the ADPRW command has been executed the last step
number will be retained in the device register.
Special clear conditions:
1) Power on
2) STOP to RUN
Note: If the step number is greater than 32767 the value will
become a negative number. To see the step numbers
above 32767 the user must convert the step number to
an unsigned value.
R
D8408 D8428
Current Retry
Value
M
The current value of retries that the master is sending to
process the request.
Special clear conditions:
1) Power on
2) STOP to RUN
3) Next MODBUS command
R
D8409 D8429
Slave Response
Timeout
M
After the master sends a request and no response is received
from the slave within the specified time, the master will retry to
send the message or terminate the processing of the command
with a time out error depending on the setting of the "number of
retries" (D8412, D8432).
Valid values: 0 to 32767[ms]
0 will default the timeout to 3 seconds
Note: This value can also be changed before each command
execution.
R,W
Special Data
Register
Name Valid Detailed description R / W
CH1 CH2