5. Loop Instruction Design Examples M1000 P0 Y0 Y10 Y0 Subroutine for draining water and enabling alarm when the level is above the upper bound. T0 X0 SRET M1000 P10 Y1 Y10 Y1 Subroutine for pouring water and enabing alarm when the level is below the lower bound. T1 X1 SRET M1000 P20 Y11 Subroutine for enabling mechanical failure alarm. SRET Program Description: z When the level is above the upper bound, X0 will be ON to execute [CALL P0] instruction. The abnormal situation alarm Y10 and the draining valve Y0 will start working until the level is below the upper bound. z When the level is below the lower bound, X1 will be ON to execute [CALL P10 ] instruction.
The abnormal situation alarm Y10 and the pouring valve Y1 will start working until the level is above the lower bound. z CALL P20 subroutine is nested both in P0 and P10 subroutines. If the upper bound sensor is still on after draining water for 10 minutes, subroutine P20 will be executed. Coil Y11 will be ON and the mechanical failure alarm will be enabled. z Likewise, if the lower bound sensor is still ON after pouring water for 5 minutes, subroutine P20 will be executed. Coil Y11 will be ON and the mechanical failure alarm will be enabled. z If the level is at normal position, X0 = OFF, X1 = OFF, ZRST instruction will be executed. Y0, Y1, Y10, Y11, T0, and T1 will be reset.
All valves as well as alarms will be disabled. DVP-PLC Application Examples 5-4 TMR T0 K6000 CALL P20 TMR T1 K3000 CALL P20