3 Communications Protocols
3.2.1 Extended MEMOBUS Protocol
3-4
3.2 Protocol Functions
3.2.1 Extended MEMOBUS Protocol
The Extended MEMOBUS protocol is used between Controllers with the 218IF Module. It
can also be used between 215IF Modules.
From a functional point of view, Extended MEMOBUS provides extended functions over the
MEMOBUS protocol using conventional RS-232C communications. A wider range of func-
tions and more efficient communications are provided than with the MEMOBUS protocol.
The MEMOBUS mode and the general-purpose message mode are available with the
Extended MEMOBUS protocol. These are specified in the parameters of the send message
and receive message functions (MSG-SND and MSG-RCV).
Extended MEMOBUS Protocol Functions
The functions provided by the Extended MEMOBUS protocol are shown in the following
table.
Table 3.2 Extended MEMOBUS Protocol Functions
Function
Code
Function No. of Points Remarks
01H Coil status read 2,000 points
−
02H Input relay status read 2,000 points
−
03H Holding register write 125 words
−
04H Input register write 125 words
−
05H Single coil status change 1 point
−
06H Single holding register write 1 word
−
08H Loopback
−−
09H Holding register read (extended) 508 words
−
0AH Input register read (extended) 508 words
−
0BH Holding register write (extended) 507 words
−
0DH Discontinuous multiple holding register read (no
header)
508 words
−
0EH Discontinuous multiple holding register write 254 words
−
0FH Multiple coil status change 800 points
−
10H Multiple register write 100 words
−
31H MELSEC fixed buffer communications 507 words
218IF only
32H MELSEC random buffer read 508 words
218IF only
33H MELSEC random buffer write 507 words
218IF only
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