7. COMMUNICATION THAT DO NOT REQUIRE
THE SEQUENCE PROGRAM
MELSEC-A
7-14
7.1.10 Reading device memory and buffer memory (Read: Server)
A "Read" service is issued by the client to read the PC CPU device memory and special functions
module buffer memories.
The device memories to be read must be registered in advance in the OD as an Array, Simple
Variable, or Record using the software package. In addition, the buffer memory must be registered in
the OD as an Array or Simple Variable.
[Parameters required by the client]
•
Access Specification
Read device specifications are executed by Index or Name.
Access Specification
Setting value
Index
Index of the variable to be read
Variable Name
Name of the variable to be read
•
Subindex
This specifies which element will be read when an Array or Record is read.
If a Subindex is not specified then all the elements will be read.
The Array or Record header element Subindex is 1.
[Server (AJ71PB96F/A1SJ71PB96F) answer parameters]
•
Data
This sets the value of the variable to be read.
The data arrangement when a bit-String is conducted using the following specifications, so
be careful.
When accessing from the M100 using a 16 unit bit-String
M115
M114
M113
M112
M111
M110
M109
M108
1
0
LSB
MSB
M107
M106
M105
M104
M103
M102
M101
M100
In addition, in PROFIBUS-FMS the unit used to read Bit-String data is 8 bits. In other words,
bit lengths that do not equal multiples of 8, such as 3 bits or 4 bits, are not read.
