Chapter 3 Message Format; Message Format; How To Understand Command Descriptions - Mitsubishi Electric MELSEC iQ-F Series FX5 User Manual

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MESSAGE FORMAT

This chapter describes the message data format, the data specification method, and limitations etc. when performing SLMP
data communication using the 3E frame to the built-in Ethernet port.
Frame type
3E frame
3.1
Message Format
This section describes the message format for each command when performing the data communication using the 3E frame.

How to understand command descriptions

This section describes how to understand message diagrams in each command description shown in Page 43 Device
Access and after.
The following example shows how to understand message diagrams in command descriptions for each control procedure
when communicating with the built-in Ethernet port.
When data is read from a CPU module by external equipment
(Command message)
E
External
N
Part A
equipment
Q
CPU module
• Part A indicates transfer from the external equipment to the CPU module.
• Part B indicates transfer from the CPU module to the external equipment.
• Create a program in the external equipment so that each data is transferred sequentially from the left to the right.
Ex.
In part A, data is sent sequentially starting from ENQ. In part B, data is received sequentially starting from STX.
When data is written from external equipment to a CPU module
E
External
N
Part C
equipment
Q
CPU module
• Part C indicates transfer from the external equipment to the CPU module.
• Part B indicates transfer from the CPU module to the external equipment.
• Create a program in the external equipment so that each data is transferred sequentially from the left to the right.
Ex.
In part C, data is sent sequentially starting from ENQ. In part B, data is received sequentially starting from ACK.
After receiving a command message from the external equipment, the CPU module completes the processing
for part A and part C in the message and sends a response message part B, then starts the receiving wait
status (neutral status).
Built-in Ethernet port
Communicable
S
T
Part B
X
(Response message)
A
C
Part B
K
(Response message)
Remark
The message format is the same as the QnA compatible 3E frame
3 MESSAGE FORMAT
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3.1 Message Format
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