4 - 21 4 - 21
MELSEC-Q
4 THE EXCHANGE BETWEEN THE PLC AND BUFFER MEMORY
• For character data
Buffer Memory
PLC CPU Device
44
H
(H)
31
H
(H)
41
H
(L)
35
H
(L)
48
H
(L)
0D
H
(H)
D1
D2
D3
GETMEM
/PUTMEM
AD51H-BASIC Side
41
H
(L)
44
H
(H)
31
H
(H)
35
H
(L)
48
H
(L)
0D
H
(H)
10
H
11
H
12
H
20
H
21
H
22
H
23
H
24
H
25
H
FROM
/TO
PLC CPU Side
A
D
5
1
H
<CR>
41
H
= "A"
44
H
="D"
35
H
= "5"
31
H
= "1"
48
H
= "H"
0D
H
=CR code
( )
Accessed using
address 10
H
through 12
H
1st
character
2nd
character
3rd
character
4th
character
5th
character
6th
character
( )
Accessed using
address 20
H
through 25
H
Stores the value of the buffer
memory using character codes.
Character Variables, Character Array Variables
RD $
The PUTMEM and GETMEM instructions are used in common memory and while sharing
access of internal devices (ED).
Note that when addresses 1800h through 7FFFh (viewed from BASIC) are used,
the process will be performed on the common memory and internal device.
• When reading data with the GETMEM instruction, the following illustrates if a
character data greater than the character variable specified as readout variables or
number of bytes to be read in the character array variables (one byte = one
character) is stored.
When RD$ is used as the readout variable
RD$
. M. I. T. S. U. B. I. S. H. I.
. A. D. 5. 1. H.
. A. D. 5. 1. H. B. I. S. H. I.
RD$
Readout data
Readout execution
Data before the readout
execution will be stored
REMARK
Access • • • A collective term for I/O processing such as reading and writing data.
