Technical data

6.31.3
OB 241: Processing
Shift Registers
The special function organization block OB 241 processes a shift
register providing it has been initialized by OB 240.
In the CPU 928B, you can call a maximum of 64 shift registers.
Application Before you call OB 241, certain flag bits are usually set/reset in the
pointers.
Each time OB 241 is called, the information is shifted byte by byte
from one memory cell to the next higher memory cell. The pointers
are then supplied with new contents. By repeatedly calling OB 241,
the information can be shifted through the complete shift register to
the last memory cell. From here, it is then transferred to memory
cell 1.
Function Each time OB 241 is processed, the shift register addressed via
ACCU-1-L is shifted one position to the right.
Parameters ACCU-1-L
Number of the shift register to be processed,
permissible values: 192 to 255
Result After you call OB 241, the pointers (maximum 6 per shift register)
that can be positioned as required with the exception of the base
pointers contain the information of the preceding memory cell. You
can then evaluate this information.
Possible errors
•• illegal shift register number in ACCU 1
•• shift register not initialized.
In the event of an error, the CPU recognizes a runtime error and calls
OB 31. What happens then depends on how you have programmed
OB 31 (see Section 5.6.2). If OB 31 is not loaded, the CPU goes to the
stop mode.
In both cases, error IDs are entered in ACCU-1-L that describe the
error in greater detail.
OB 240 to 242: Special Functions for Shift Registers
CPU 928B Programming Guide
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