
16-4
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 Left Double
Word instruction. This instruction shifts bits 0 to 31 of input IN bit by bit to
the left. Input N specifies the number of bits by which to shift. If N is larger
than 32, 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 right 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 CC 0 and OV
bits of the status word to 0 if N is not equal 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 Left Double Word box
(see Section 6.1).
Table 16-2 Shift Left Double Word Box and Parameters
LAD Box Parameter Data Type Memory Area Description
EN BOOL I, Q, M, D, L Enable input
_
EN ENO
ENO BOOL I, Q, M, D, L Enable output
IN DWORD I, Q, M, D, L Value to shift
N
N WORD I, Q, M, D, L Number of bit positions by which to shift
OUT DWORD 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 double word MD0 is shifted to the left by
the number of bits specified in memory word
MW4.
The result is put into memory double word
MD10. If the signal state of the bit shifted last
was 1, output Q 4.0 is set.
Q 4.0
SHL_DW
N
OUT
EN ENO
MW4
IN
Function is executed (EN = 1):
MD10MD0
S
Figure 16-2 Shift Left Double Word
Shift Left Double
Word
Shift and Rotate Instructions
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