Down counter

CTD - Down counter

Symbol:

Description:
Upon a FALSE-TRUE transition of a rung, the down counter decrements it's internal counter by one. A preset value is assigned as Kn, where n is an integer value. When the current counter value is greater than the preset value, the counter done bit is set TRUE. Then the current counter value is less than the preset value, the counter done bit is set FALSE.

Note: The CTD may only be used in conjunction with the CTU, and must be the rung directly following the CTU. The CTD and CTU will share the same counter number (ie. CT0) as well as preset value (Kn).

Range:

CT0-CT7
K0-Kmax

Memory Map

Type: Boxes (Counters/Timers)