Allen-Bradley PLC-2/30

Bit Shifts
Chapter 14
148
This condition instruction examines a user specified bit in a bit shift
register, such as shown in Figure 14.1, for an on or 1 condition. The
instruction can be used alone or in conjunction with other input
instructions to affect the rung decision.
Instruction overview:
Input instruction
Key sequence: [SHIFT REG] 19
3 words of users program required
To program an Examine On Shift Bit instruction press [SHIFT REG] 19.
A display represented by Figure 14.6 will appear.
Figure 14.6
EXAMINE
ON SHIFT BIT Format
EXAMINE ON
SHIFT BIT
FILE: 110
BIT NO.: 001
Numbers shown are default values. Bold numbers must be replaced by userentered values. The number of default address digits
initially displayed  3, 4, or 5  will depend on the size of the data table. Initially displayed default values are governed by the I/O rack
configuration.
FILE : Starting address of the file (file of bit shift instruction).
BIT NUMBER : Decimal number of the bit to be examined (1999).
Figure 14.7 shows the format of Figure 14.6 for the following conditions
of the bit shift register of Figure 14.1.
File – Starts at word 400
Bit No. – Examine bit number 67 in the shift register for an on (1)
condition.
14.4
Examine On Shift Bit
14.4.1
Programming Examine On
Shift Bit Instruction
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