Technical data

Initializing When you initialize a shift register (see Section 6.31.2), you specify
the number of the flag byte for pointer 1 (= base pointer). This is then
set permanently on the first memory cell of the shift register. You then
position all the other pointers relative to the base pointer (you can use
between one and a maximum of six pointers per shift register).
Shifting When you shift a shift register (like a hardware shift register), the total
contents of all the shift register cells are transferred in bytes from one
memory cell to the next (see Fig. 6-17). Each time the shift register
function is called, the information is shifted one memory cell
(corresponds to one clock pulse), and the pointers are supplied with
new contents. As shown by the arrows, the information is shifted
through the complete shift register to the last memory cell from where
it returns to memory cell 1 (after 12 clock pulses for the shift register
illustrated in the schematic).
Pointer 1 Pointer 2 Pointer 3
Bit 0
Bit 1
Bit 2
Bit 3
Bit 4
Bit 5
Bit 6
Bit 7
123456 789101112
Flag bit 0
Flag bit 1
Flag bit 2
Flag bit 3
Flag bit 4
Flag bit 5
Flag bit 6
Flag bit 7
Fig. 6-16 Schematic showing the principle of a shift register with 3 pointers and 12 memory cells
OB 240 to 242: Special Functions for Shift Registers
CPU 928B Programming Guide
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