Interlock

Two seal-ins, forward and reverse, each with a normally closed contact on the other output.

Step by step

Pick a step. The rungs are drawn by the editor after Core scans the program up to that step.

Global.FwdPB

Global.MotorFwd

Global.StopPB

Global.MotorRev

Global.MotorFwd

Global.RevPB

Global.MotorRev

Global.StopPB

Global.MotorFwd

Global.MotorRev

1. Press FwdPB. Rung 0 is true and MotorFwd turns on. In rung 1, XIO MotorFwd now blocks power.

Step	FwdPB	RevPB	StopPB	MotorFwd	MotorRev
1. Press FwdPB	1	0	0	1	0
2. Release FwdPB	0	0	0	1	0
3. Press RevPB	0	1	0	1	0
4. Press StopPB	0	0	1	0	0
5. Press RevPB	0	1	0	0	1
6. Press FwdPB	1	0	0	0	1

Each rung is a seal-in with one extra XIO, on the other output.
An XIO passes power only while its tag is 0. When MotorFwd is 1, XIO MotorFwd in rung 1 blocks MotorRev, and the other way round.
The rungs run from top to bottom. If both buttons are pressed in the same scan from stopped, rung 0 runs first and MotorFwd wins. Rung 1 then reads MotorFwd as 1.

Interlocking on the buttonsXIO RevPB in the forward rung only blocks while the button is held. Interlock on the outputs, MotorFwd and MotorRev.
Reversing without stoppingThe interlock forces a Stop between directions. Add a timer after Stop if the machine needs time to come to rest.