3 Communications Protocols
3.2.3 MELSEC-A Protocol
3-8
Fig. 3.3 MELSEC Format Message Flow
Between a Controller and MELSEC-A
MELSEC Commands Supported by the 217IF
The following table shows the common MELSEC ACPU commands supported by the
MP900-Series 217IF Module, and the MEMOBUS command codes corresponding to these
commands.
Note: Special AnACPU commands are not supported. Use the common
ACPU commands for AnACPU access. AnACPU expansion registers
cannot be accessed.
CPU
MP900-Series Controller
MELSEC format
Ethernet
MSG-SND
217IF/
218IF
MELSEC-A
MSG-RCV
A2UCPU
AJ71E71
AJ71UC24
Table 3.3 Common MELSEC ACPU Commands
MEMOBUS
Command
MELSEC
Command
Description Qty Remarks
01H/02H WR Reads bit devices in 16-point units 32 words (512 points)
−
03H/04H Reads word devices in 1-point units 64 points
−
0FH WW Writes bit devices in 16-point units 10 words (160 points)
−
10H Writes word devices in 1-point units 64 points
−
08H TT Loopback test 254 characters
−
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