83Plus:BCALLs:4F4B

Synopsis

Unofficial Name: RejectCommand

BCALL Address: 4F4B

Finishes receiving a silent link command and then rejects it by sending an acknowledgement packet and then the skip/exit packet with a value of 5, then receiving an acknowledgement.

Inputs

• E: zero
• A: current value of port 0
• set 0,(iy+3Eh) if link assist is active

Outputs

• 4 bytes received to header
• A: second byte received

Destroys

• All

Comments

This is the link activity hook used by the OS. "add a,e" is actually run when you BCALL it, so make sure E is zero. I can't fathom why they did this. To activate it in the OS, send 73h,29h,00h,00h to the calculator. To deactivate it (or any link activity hook), send 73h,3Ah,00h,00h.

You also probably should not call it unless you have detected link activity (for use in the link activity or silent link hooks).

It will not send the skip/exit packet when receiving the ready packet; it only acknowledges it.