RevokeBoardAvailable when PCB Manually removed.

[Industry4]

User Comment

During the test, when there is a problem, we hope that when the This Station / ScanStation board information is manually deleted, can it automatically send a [RevokeBoardAvailable]?

Notify the downstream device that the current state needs to be changed, otherwise the two devices will lock each other

[Industry4]

1. Normal Sequence

SMEMA	Data	This Station	Downstream
HIGH	Y		Machine Ready
HIGH	Y	Board Available
HIGH	Y		Start Transport
LOW	N	Transport Finished
LOW	N		Stop Transport

2. Data Deleted by User After Board Available

SMEMA	Data	This Station	Downstream
HIGH	Y		Machine Ready
HIGH	Y	Board Available
HIGH	N	Revoke Board Available
HIGH	N		Start Transport
LOW	N	Transport Finished
LOW	N		Stop Transport

3. Data Deleted by User After Start Transport

SMEMA	Data	This Station	Downstream
HIGH	Y		Machine Ready
HIGH	Y	Board Available
HIGH	Y		Start Transport
HIGH	N
LOW	N	TF - Transfer Incomplete
LOW	N		Stop Transport

[Industry4]

There were multible options to resolve this issue:

1. Prevent the deletion of Data when a Transfer is occurring. We didn't do this as a operator may want to stop a transfer.
2. Use 'Revoke Board Available' (Sequence 2 above) however a 'Board Available' is only sent following a 'Machine Ready' and that will be shortly followed by a 'Start Transport'. By this point a 'Revoke Board Available' is too late.
3. Solution: Sequence 3 (above) above is more likely so we send a 'Transport Finished' with a Transfer State of Incomplete.

The actual 'lock' as described in the issue description was caused by the 'Transport Finished' message being sent with Null values (Bug)