udc dl06

I took this quote from a previous thread back in 2006 using directsoft software with dl06 plc

"When I use mode 20 from which I could figure a way to tell direction even without the special relays the count does not go into the negative numbers at CTA174. It appears that when it counts down to zero it then goes to a positive 8 million something which cause the counter to reset over and over. If they say counter is from a negative value to the positive value, why can't I get it to count both ways (going into negative numbers after counting down to zero."

Instead of seeing the 8 million something in counter. make the counter read -1, -2 -3 etc or better yet see 0, 99, 98 etc

by changing the value to decimal in the online menu bar I see the value change to negative but the counter value reads 8 million something

any thoughts

Counters in the Directlogic PLCs are represented by BCD numbers. BCD numbers do not have a way to represent negative numbers since there is not a designated sign bit.

sorry for the delay but thanks for the reply...

Instead of pulling my hair out watching the counter acc switch to 8 million something, I used a little math with some v-memory locations to get the results I needed