Index

PSIM
PLC Counters
Introductory Lab


 

CTU and RES Instructions

  • From the Main Menu of the PSIM program, select the I/O simulation display.
  • Toggle Function Key [F2] until the minimum I/O Data Table is displayed in the upper box of the display, and the Counter Table is displayed in the lower box of the Data table display.
  • Select the Rung Editor [F5] and enter the following ladder Logic program.

Once you have entered your program, select the Program Utility menu and save your program to disk. Now exit the Rung Editor and return to the I/O simulation Display.

Note the initial value of counter C1's accumulator, preset and the state of its done, enable and zero bits.

Note: the zero bit "CZ" is not shown in the data table display but its state is reflected by light O:1/01.

C1:A = __________ C1:P = __________ C1/DN = ____ C1/CU = ____ C1/CZ=____

  • Open and Close switch I:1/00 a number of times and carefully observe the incrementing of C1's accumulator and the operation of the zero, enable and done bits.
  • Close switch I:1/01 and observe the effect that the "RES" instruction has on the counter.
  • Attempt to increment the counter while switch I:1/01 is closed. You should not be able to increment the counter while the "RES" instruction is held "True".
  • Open switch I:1/01 to allow the "RES" instruction to go false and then increment the counter until the accumulator matches the preset.
  • Increment the counter 2 or 3 more times and note the final value of C1's accumulator, preset and status bits.

C1:A = __________ C1:P = __________ C1/DN = ____ C1/CU = ____ C1/CZ=____

 

 

CTD Instruction

Ensure that switch I:1/00 and I:1/01 are open; then Select (F5) the Rung Editor and modify your program so that it matches the following:

  • Once you have completed your program, save it to disk and return to the I/O simulation display.
  • Toggle the state of switch I:1/00 continuously until the accumulator of C1 exceeds the preset.
  • Now toggle switch I:1/02 and decrement counter C1 while carefully observing the status bits of the counter.
  • Increment and decrement the counter from below zero to beyond the preset a number of times.

 

 

 

 

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