40
5756B
Functions Called in the OB 1
Functions FC 21 to read I/O data and FC 22 to write I/O data
are called in the OB 1.
Read Function FC 21 MEM_READ
Call Description:
Function FC 21 MEM_READ reads consistent data blocks
(data records) from the controller board buffer and copies
them to the selected address area of the PLC.
Program Sequence of FC 21:
Parameter Descriptions:
AN
M10.0
S
M10.0
CALL
FC21
// Call read function
IBDB
:= DB20
// INTERBUS data block
MODE
:= 1
// Function operating mode
SOURCE
:= 0
// Not used
DEST_AREA
:= 0
// Not used
DEST_AREA_NR
:= 0
// Not used
DEST_OFFSET
:= 0
// Not used
DEST_LENGTH
:= 0
// Not used
RET
:= M10.1 // Result bit
BUSY
:= M10.0 // Activate FC 21
Parameter
Value Meaning
IBDB
DB 20 Global INTERBUS data block
MODE
1
Read data record 1 (set in
IBS CMD)
SOURCE
0
Not used
DEST_AREA
0
Not used
DEST_AREA_NR
0
Not used
DEST_OFFSET
0
Not used
DEST_LENGTH
0
Not used
RET
M10.1 = 0: The function was
executed without errors.
= 1: An error occurred.
BUSY
M10.0 Activate FC 21