Siemens SIMATIC S5-90U, Системное руководство

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STEP 5 Operations S5-90U/S5-95U
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 (IB 7 and IB 8) are loaded from the PII into the accumulator.
Loading does not change the PII (see Figure 8-2).
Figure 8-2. Execution of the Load Operation
Byte a
Byte c
L IB 8
L IB 7
Information
from the PII Lost
information
0 IB 7
ACCU 2 ACCU 1
Byte b
Byte d IB 7
Byte d Byte c Byte a
Byte b IB 7 0
Byte b
Byte a
0 IB 8 IB 8
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.
When transfer to the digital output area occurs, the byte or word in question in the PIQ is
automatically updated.
Example: Figure 8-3 shows how byte a, the low byte in ACCU 1, is transferred to QB 5.
Figure 8-3. Transferring a Byte
T QB 5
Information
in the PIQ Lost
information ACCU 2 ACCU 1
Byte d Byte c Byte a
Byte d
Byte b
Byte c Byte a Byte a Byte b
Previous value
of QB 5
8-12
EWA 4NEB 812 6115-02b