
6-5
Ladder Logic (LAD) for S7-300 and S7-400
C79000-G7076-C504-02
Table 6-6 lists the maximum address ranges for various memory areas. For
the address range possible with your CPU, refer to the appropriate S7-300
CPU manual.
Table 6-6 Memory Areas and Their Address Ranges
Access to Area
ame o
rea
via Units of the Following Size: Abbrev.
Maximum Address Range
Process-image input Input bit
Input byte
Input word
Input double word
I
IB
IW
ID
0.0 to 65,535.7
0 to 65,535
0 to 65,534
0 to 65,532
Process-image
output
Output bit
Output byte
Output word
Output double word
Q
QB
QW
QD
0.0 to 65,535.7
0 to 65,535
0 to 65,534
0 to 65,532
Bit memory Memory bit
Memory byte
Memory word
Memory double word
M
MB
MW
MD
0.0 to 255.7
0 to 255
0 to 254
0 to 252
Peripheral I/O:
External input
Peripheral input byte
Peripheral input word
Peripheral input double word
PIB
PIW
PID
0 to 65,535
0 to 65,534
0 to 65,532
Peripheral I/O:
External output
Peripheral output byte
Peripheral output word
Peripheral output double word
PQB
PQW
PQD
0 to 65,535
0 to 65,534
0 to 65,532
Timer Timer (T) T 0 to 255
Counter Counter (C) C 0 to 255
Data block
Data block opened with the statement DB
––(OPN)
Data bit
Data byte
Data word
Data double word
DBX
DBB
DBW
DBD
0.0 to 65,535.7
0 to 65,535
0 to 65, 534
0 to 65,532
Data block opened with the statement DI
––(OPN)
Data bit
Data byte
Data word
Data double word
DIX
DIB
DIW
DID
0.0 to 65,535.7
0 to 65,535
0 to 65, 534
0 to 65,532
Local data Temporary local data bit
Temporary local data byte
Temporary local data word
Temporary local data double word
L
LB
LW
LD
0.0 to 65,535.7
0 to 65,535
0 to 65, 534
0 to 65,532
Configuration and Elements of Ladder Logic
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