Related Devices And Communication Status; Special Data Registers - Mitsubishi FX3U Series User Manual

FX Series Programmable Controllers
3U
User's Manual - MODBUS Serial Communication Edition
6.

Related Devices and Communication Status

In this section the device numbers and functions of the special data registers and special auxiliary relays are
described for MODBUS serial communication.
6.1

Special Data Registers

The table shows the Special Data registers used in MODBUS serial communication.
Special Data
Register
CH1 CH2
D8400 D8420
D8401 D8421 Protocol
D8402 D8422
D8403 D8423 Error Details
D8404 D8424
32
Name Valid
Communication
M, S
Format
M, S
Communication
M, S
Error Code
M, S
Error step
M
number
6 Related Devices and Communication Status
Detailed description
This device sets the communication format.
Note: For details on communication format refer to Section 6.2.
Selection of the channel used, RTU or ASCII mode and Master
or Slave identification.
Bit No. Name
Protocol Other communication
b0
Selection protocol
b1-3 Not used
Master/ slave
b4 MODBUS Master
setting
b5-7 Not used
RTU/ASCII
b8 RTU
mode setting
b9-15 Not used
Note: When both flags (b0 of D8401 and b0 of D8421) are
turned on, priority will be given to CH1 and CH2 will no
longer operate.
Current error code generated by the MODBUS function.
Special clear conditions:
1) Power on
2) STOP to RUN (master only)
Current error details.
Special clear conditions:
1) Power on
2) STOP to RUN (master only)
Note: Refer to the Error table in Chapter 12.
STEP number of the first ADPRW command that caused the
original error.
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.
6.1 Special Data Registers
Contents
0 (bit = OFF) 1 (bit = ON)
MODBUS
serial line
MODBUS
Slave
ASCII
R / W
*1
R,W
*1
R,W
R,W
R,W
R,W