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Shift Instructions Section 5-16
5-16 Shift Instructions
5-16-1 SHIFT REGISTER – SFT(10)
Limitations E must be greater than or equal to St, and St and E must be in the same data
area.
If a bit address in one of the words used in a shift register is also used in an
instruction that controls individual bit status (e.g., OUT, KEEP(11)), an error
(“COIL/OUT DUPL”) will be generated when program syntax is checked on the
Programming Console or another Programming Device. The program, how-
ever, will be executed as written. See Example 2: Controlling Bits in Shift Reg-
isters for a programming example that does this.
Description SFT(10) is controlled by three execution conditions, I, P, and R. If SFT(10) is
executed and 1) execution condition P is ON and was OFF the last execution,
and 2) R is OFF, then execution condition I is shifted into the rightmost bit of a
shift register defined between St and E, i.e., if I is ON, a 1 is shifted into the
register; if I is OFF, a 0 is shifted in. When I is shifted into the register, all bits
previously in the register are shifted to the left and the leftmost bit of the regis-
ter is lost.
The execution condition on P functions like a differentiated instruction, i.e., I
will be shifted into the register only when P is ON and was OFF the last time
SFT(10) was executed. If execution condition P has not changed or has gone
from ON to OFF, the shift register will remain unaffected.
St designates the rightmost word of the shift register; E designates the left-
most. The shift register includes both of these words and all words between
them. The same word may be designated for St and E to create a 16-bit (i.e.,
1-word) shift register.
When execution condition R goes ON, all bits in the shift register will be
turned OFF (i.e., set to 0) and the shift register will not operate until R goes
OFF again.
Flags There are no flags affected by SFT(10).
St: Starting word
IR, SR, AR, HR, LR
E: End word
IR, SR, AR, HR, LR
Operand Data Areas
Ladder Symbol
I
P
SFT(10)
St
E
R
Execution condition I
Lost data
E
St+1, St+2, ... St
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