Message Communications; Memobus Message Transmissions - YASKAWA MP920 User Manual

2.3

Message Communications

This section explains message communications.
Message communications are used to transfer messages between Machine Controllers one event
at a time using the MESSAGE SEND function (MSG-SND) and the MESSAGE RECEIVE
function (MSG-RCV). The following two transmission modes are available:
• MEMOBUS message transmission mode
• General-purpose message transmission mode
2.3.1

MEMOBUS Message Transmissions

MEMOBUS messages can be transmitted and received by user programs, and are transmit-
ted using the MEMOBUS protocol.
The Master transmits MEMOBUS messages to the Slaves using the MSG-SND function,
and the Slaves return response messages using the MSG-RCV function. The MEMOBUS
message flow is shown below.
ST#1
PS-01
Data is transmitted to ST#2 via the line from the ST#1 using the MESSAGE SEND function
(MSG-SND).
The ST#2 uses the MESSAGE RECEIVE function (MSG-RCV) to read the data from the
specified registers and return a response to ST#1.
The processing results can be checked in MSG-SND PARAM (parameter area).
CPU-01
Commu-
nications
Module
Parameters
MSG-SND
Transmission device: 215IF,
217IF, and 218IF
EXECUTE BUSY
Communications protocol:
ABORT COMPLETE
MEMOBUS
ERROR
PARAM
2-5

2.3 Message Communications

ST#2
PS-01 CPU-01
Commu-
nications
Module
MSG-RCV
EXECUTE BUSY
COMPLETE
ABORT
PARAM
2