Quick Reference
Appendix E
E-7
Important: The counter word address, XXX, is assigned to the counter
accumulated areas of the data table. To determine which addresses are
valid accumulated areas, the third digit from the right must be an
even number.
This Bit:
Contains This Information:
14
overflow/underflow bit
15
count complete bit
16
enable bit for CTD instruction
17
enable bit for CTU instruction
The word address displayed will be 3 or 4 digits long depending on the
data table size. When entering the word address, use a leading zero
if necessary.
Key
Symbol
Instruction
Name
1770T3
Display
Rung Conditions
Status Bits
-(CTU)-
Up Counter
XXX
-(CTU)-
PR YYY
AC ZZZ
Each time the rung goes true, the
accumulated value is incremented one
counter. The counter continues counting
after the preset value is reached.
The accumulated value can be reset by
the CTR instruction
When the rung is true:
If AC> 999 bit 14 is set
When AC
≥
PR bits 15 and 17 are set
When the rung is false:
Bit 14 and 15 are retained;
if they were set, bit 17 is reset
-(CTR)-
Counter Reset
XXX
-(CTR)-
PR YYY
AC ZZZ
XXX - Word address of the CTU
is resetting.
The preset and accumulated values are
automatically entered by the industrial
terminal. When the rung is true the CTU
and CTD accumulated value and status
bits are rest to 000.
When the rung is true:
Bits 14, 15, 16, 17 are reset
When the rung is false:
No action is taken
-(CTD)-
Down Counter
XXX
-(CTD)-
PR YYY
AC ZZZ
Each time the rung goes true, the
accumulated value is decreased by
one count.
When the rung is true:
AC is < 000
Bit 14 is set
When AC<PR bits 15 and 16 are set
When the rung is false:
Bits 14 and 15 are retained;
if they were set, bit 16 is reset
Counter Instructions
