GFK-0467K Chapter 4 Series 90-30/20/Micro Instructions Set 4-77
4
SHFR (BIT, WORD) Use the Shift Register (SHFR) function to shift one or more data words or data bits from a reference
location into a specified area of memory. For example, one word might be shifted into an area of
memory with a specified length of five words. As a result of this shift, another word of data would
be shifted out of the end of the memory area.
Note
When assigning reference addresses, overlapping input and output reference
address ranges in multi-word functions may produce unexpected results.
The SHFR function has four input parameters and two output parameters. The reset input (R) takes
precedence over the function enable input. When the reset is active, all references beginning at the
shift register (ST) up to the length specified for LEN, are filled with zeros.
If the function receives power flow and reset is not active, each bit or word of the shift register is
moved to the next highest reference. The last element in the shift register is shifted into Q. The
highest reference of the shift register element of IN is shifted into the vacated element starting at
ST. The contents of the shift register are accessible throughout the program because they are
overlaid on absolute locations in logic addressable memory.
The function passes power to the right whenever power is received through the enable logic.
_____
| |
(enable) —|SHFR_|— (ok)
| |
| WORD|
| |
(reset) —|R Q|— (output parameter Q)
| LEN |
|00001|
| |
| |
| |
(value to be shifted) —|IN |
| |
| |
| |
(first bit or word) —|ST |
|_____|