
16-5
Ladder Logic (LAD) for S7-300 and S7-400
C79000-G7076-C504-02
A signal state of 1 at the Enable (EN) input activates the Shift Right Word
instruction. This instruction shifts bits 0 to 15 of input IN bit by bit to the
right. Bits 16 to 31 are not affected. Input N specifies the number of bits by
which to shift. If N is larger than 16, the command writes a 0 in output 0 and
resets the CC 0 and OV bits of the status word to 0. The bit positions at the
left are padded with zeros. The result of the shift operation can be scanned at
output OUT.
The operation triggered by this instruction always resets the OV bit of the
status word to 0. If the box is executed (EN = 1), ENO shows the signal state
of the bit shifted last (same as CC 1 and RLO in the status word). The result
is that other functions following this box that are connected by the ENO
(cascade arrangement) are not executed if the bit shifted last had a signal
state of 0.
Certain restrictions apply to the placement of the Shift Right Word box (see
Section 6.1).
Table 16-3 Shift Right Word Box and Parameters
LAD Box Parameter Data Type Memory Area Description
EN BOOL I, Q, M, D, L Enable input
_
ENO BOOL I, Q, M, D, L Enable output
IN WORD I, Q, M, D, L Value to shift
N WORD I, Q, M, D, L Number of bit positions by which to shift
O WORD I, Q, M, D, L Result of shift operation
Status Word Bits
BR CC 1 CC 0 OV OS OR STA RLO FC
Write x x x x – x x x 1
I 0.0
A signal state of 1 at input I 0.0 activates the
instruction.
Memory word MW0 is shifted to the right by the
number of bits specified in memory word MW2.
The result is put into memory word MW4. If the
signal state of the bit shifted last was 1, output
Q 4.0 is set.
Q 4.0
SHR_W
N
OUT
EN ENO
MW2
IN
Function is executed (EN = 1):
MW4
MW0
S
Figure 16-3 Shift Right Word
Shift Right Word
Shift and Rotate Instructions
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