Installation manual

Publication 1747-RM001G-EN-P - November 2008
Application Specific Instructions 7-3
Status bits of the control element may be addressed by mnemonic. They
include:
– Unload Bit UL (bit 10) stores the status of the bit exited from the
array each time the instruction is enabled.
– Error Bit ER (bit 11), when set, indicates the instruction detected an
error such as entering a negative number for the length or position.
Avoid using the output bit when this bit is set.
– Done Bit DN (bit 13), when set, indicates the bit array has shifted
one position.
– Enable Bit EN (bit 15) is set on a false-to-true transition of the rung
and indicates the instruction is enabled.
When the register shifts and input conditions go false, the enable, done,
and error bits are reset.
• Bit Address is the address of the source bit that the instruction inserts
in the first (lowest) bit position (BSL) or the last (highest) bit position
(BSR).
• Length (size of bit array) is the number of bits in the bit array, up to
2048 bits. A length value of 0 causes the input bit to be transferred to
the UL bit.
A length value that points past the end of the programmed file causes a
runtime major error to occur.
The instruction invalidates all bits beyond the last bit in the array (as defined
by the length) up to the next word boundary
TIP
If you alter a length value with your ladder program,
make certain that the altered value is valid.
TIP
If a String element address is used for the file
parameter, the maximum length for SLC 5/03 and
higher processors is 672 bits. Additionally, String
element boundaries cannot be crossed.