Allen-Bradley MicroLogix 1400 Instruction Manual page 186

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184 Timer and Counter Instructions
CTD Instruction Counter Control and Status Bits, Counter Word 0
(Data File 5 is configured as a timer file for this example.)
Bit
bit 11 - C5:0/UN UN - underflow
indicator
bit 13 - C5:0/DN DN - done
indicator
bit 14 - C5:0/CD CD - count down
enable
Publication 1766-RM001A-EN-P - October 2008
Is Set When:
the accumulated value wraps from
-32,768...+32,767 and continues to count
down
≥
accumulated value preset value
rung state is true
And Remains Set Until One of the Following
Occurs:
a RES instruction with the same address as the
CTD instruction is enabled
• accumulated value
<
preset value or,
• a RES instruction with the same address as the
CTU instruction is enabled
• rung state is false
• a RES instruction with the same address as the
CTD instruction is enabled