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Chapter 7 Communication function
7-12
7.1.4 Example of user defined programming
[Figure 7.5] shows the example of communication system and frame structure between GLOFA PLC and other
company’s PLC. With the example in [Figure7.5], programming method of user defined communication will be
described. The example is for the case when writing 18 byte data of %MB0 area in GLOFA-PLC via other company’s
PLC and reading 24 byte data of other company’s PLC to save to area address of %MB100 in GLOFA-PLC.
[Figure 7.5] Example of communication system with other company’s PLC
[ A ] SYSTEM CONFIGURATION
(A) WRITE REQUEST FRAME
[BCC] [EOT] Data(18-byte) 8 1 R W [ENQ]
(B) READ DATA FRAME
[STX] R D 2 4 Data(24-byte)
[ETX] [BCC]
(C) IMMEDIATE RESPONSE FRAME
[EOT] 4 2 D R [ACK]
[ B ] STRUCTURE OF TX/RX FRAME
In [Figure7.5], 18 byte data shall be transmitted in format of (A) Write request frame from GLOFA PLC to other
company’s PLC, and (B) Read data frame along with 24 byte data is transmitted from other company’s PLC to
GLOFA-PLC. If Read data frame is received, correspondent response frame to this is transmitted in format of (C)
Immediate response frame in this protocol.
[Figure 7.5] shows data flow according to transmission sequence of frames. BCC check data is transmitted as
attached to the ends of Write/Read frames. Next is how to prepare frame and program in order to embody the
GLOFA PLC Cnet
Other com
p
an
y
’s PLC
Other company’s
PLC
RS-422 Iiterface
GLOFA-PLC