Page 221 - Programmable Logic Controllers, Fifth Edition - Mobile version

9.11 Suspend Instruction
Main program
The suspend (SUS) instruction is used to trap and iden-
Inputs
L1 tify specific conditions during system troubleshooting
SW 12 and program debugging. Figure 9-28 shows a suspend
TON EN
TIMER ON DELAY instruction in a ladder logic rung. The execution of the
Timer T4:2 DN instruction can be summarized as follows:
SW 13 Time base (sec) 1.0
Preset 5 • When you program the SUS instruction, you must
Accumulated 0
enter a suspend ID number (number 100 is used in
T4:2 LT4 this example).
• When the rung is true, the SUS output
DN instruction places the controller in the suspend
SW 13 Temporary end mode and the PLC immediately terminates
scan cycling.
TND
• All ladder logic outputs are de-energized, but other
SW 1 LT1 status files have the data present when the suspend
L instruction is executed.
• The SUS instruction writes the suspend ID number
SW 2 LT1
U (100) to S:7 as it executes.
• You can include several SUS instructions in a pro-
gram, each with a different suspend ID and read S:7
SW 3
RTO EN to determine which SUS instruction caused the PLC
RETENTIVE TIMER ON to halt.
Timer T4:3 DN
Time base (sec) 1.0 • Status file S:8 will contain the number of the pro-
Preset 50 gram file that was executing when the SUS instruc-
Accumulated 0
tion executed.
PB 1 T4:3
RES
Remainder of main program
SUS
Suspend
Suspend ID 100

Figure 9-27 Temporary end (TND) instruction. Figure 9-28 Suspend (SUS) instruction.

202 Chapter 9 Program Control Instructions

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