Technical data

Note
The number of pointers (6 including the base pointer) must not
exceed the length of the shift register.
The
distance of a pointer to the base pointer must not exceed the
length of the shift register.
Data word
DW 0 and the data word after the last pointer
distance
must always contain 0.
The data block must be open
before OB 240 is called.
The data block must have a
number in the range
DB 192 to
DB 255.
Memory requirements n = shift register length/2 + 8 data words
are required for every shift register, i.e. the length of the DB RAM is
reduced by n data words. The data block RAM end address is shifted
to lower addresses. If you attempt to initialize a shift register that
already exists, the area already assigned will be initialized again
providing the new and old shift registers both have the same length.
Otherwise the old area will be declared invalid and a new area will be
opened.
Possible errors
•• illegal data block number (<192)
•• not enough memory space in the DB RAM
•• formal error in the structure of the data block
•• illegal length specified for the shift register
•• errors in the pointer parameters
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.
6
OB 240 to 242: Special Functions for Shift Registers
CPU 928B Programming Guide
C79000-B8576-C898-01
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