Installation manual

Publication 1747-RM001G-EN-P - November 2008
Application Specific Instructions 7-7
• Control (SQO, SQC) is the control structure that stores the status byte
of the instruction, the length of the sequencer file, and the instantaneous
position in the file. You should not use the control address for any other
instruction.
Status bits of the control structure include:
– Found Bit FD (bit 08) - SQC only. When the status of all
non-masked bits in the source address match those of the
corresponding reference word, the FD bit is set. This bit is assessed
each time the SQC instruction is evaluated while the rung is true.
– Error Bit ER (bit 11) is set when the processor detects a negative
position value, or a negative or zero length value. This results in a
major error if not cleared before the END or TND instruction is
executed.
– Done Bit DN (bit 13) is set by the SQO or SQC instruction after it
has operated on the last word in the sequencer file. It is reset on the
next false-to-true rung transition after the rung goes false.
– Enable EN (bit 15) is set by a false-to-true rung transition and
indicates the SQO or SQC instruction is enabled.
• Length is the number of steps of the sequencer file starting at position
1. The maximum number you can enter is 255 words. Position 0 is the
startup position. The instruction resets (wraps) to position 1 at each
cycle completion.
The address assigned for a sequencer file is step zero. Sequencer
instructions use length + 1 word of data table files for each file
referenced in the instruction. This applies to the source, mask, and/or
destination if addressed as files.
A length value that points past the end of the programmed file causes a
runtime major error to occur.
TIP
You can address the mask, source, or destination of a
sequencer instruction as a word or file. If you address
it as a file, the instruction automatically steps through
the source, mask, or destination file.
Table 7.4 Control File Structure
15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00
Word 0 EN DN ER FD Not Used
Word 1 Length of sequencer file
Word 2 Position