Siemens SIMATIC S5-100U System Manual page 170

STEP 5 Operations
Load Operation
During loading, information is copied from a memory area, e.g., from the PII, into ACCU 1.
The previous contents of ACCU 1 are shifted to ACCU 2.
The original contents of ACCU 2 are lost.
Example: Two consecutive bytes (IB7 and IB8) are loaded from the PII into the accumulator.
Loading does not change the PII (see Figure 8-2).
Lost
information
Byte d Byte c
Byte b Byte a
Transfer Operation
During transfer, information from ACCU 1 is copied into the addressed memory area, e.g., into the
PIQ.
This transfer does not affect the contents of ACCU 1.
Example: Figure 8-3 shows how byte a, the low byte in ACCU 1, is transferred to QB5.
ACCU 2
Byte d Byte c
Byte d Byte c
8-12
ACCU 2
Byte d Byte c
Byte b Byte a
0 IB7
Figure 8-2. Execution of the Load Operation
ACCU 1
Byte b Byte a
T QB5
Byte b Byte a
Figure 8-3. Transferring a Byte
ACCU 1
Byte b Byte a
L IB7
0 IB7
L IB8
0 IB8
Information Lost
in the PIQ information
Previous value
Byte a
of QB5
EWA 4NEB 812 6120-02b
S5-100U
Information
from the PII
IB7
IB