LG GLOFA-GM Series User Manual page 270

Chapter 8 Exercising program
In [Figure 8.8], Read is requested via SND_MSG Function Block to read data and to respond to this, 20
bytes data is sent to GM_RD_ACK frame from dedicated slave station. If GM_RD_ACK frame is received,
_RCV0_232[3] is 'ON' to execute RCV_MSG Function Block and save the received data to RD_SAVE area
set to RX data variable. Memory for RD_SAVE is allocated to %MB0 area as below and data size shall be
set at least identical to the size of the received data. Next is variable setting screen of RD_SAVE which is a
saving variable of RX data.
[Figure 8.9] shows interlock program of Write data Function Block. If in normal communication, it allows
TX/RX as in sequence shown in [Figure 8.6] and even in abnormal communication, it allows communication
in the following sequence after waiting for response 1 sec.
[Figure 8.9] Interlock program to Write data
After Write request frame is executed, delete WR_START flag
and turn MON_1 flag 'ON' which turns on monitoring timer of
Write response frame.
After Write response frame is received, turn on RD_START to
send Read request frame and turn off MON_1 flag to stop frame
monitoring timer.
If no response is received for 1 sec. after Write
request frame is sent, turn on RD_START to
send Read request frame so to allow next
frame transmitted even in abnormal state
through this interlock program.
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