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Elite on the BBC Micro

Keyboard: DOVIAE [6502SP version, I/O processor]

Name: DOVIAE [Show more] Type: Subroutine Category: Keyboard Summary: Implement the #VIAE <flag> command (enable/disable interrupts)
Context: See this subroutine in context in the source code References: This subroutine is called as follows: * JMPTAB calls DOVIAE

This routine is run when the parasite sends a #VIAE <flag> command. It updates the 6522 System VIA interrupt enable register (IER) at SHEILA &4E, which allows us to enable and disable interrupts. It is used for enabling and disabling the keyboard interrupt. Arguments: A The new value of the interrupt enable register (IER)
.DOVIAE STA VIA+&4E \ Store A in SHEILA &4E JMP PUTBACK \ Jump to PUTBACK to restore the USOSWRCH handler and \ return from the subroutine using a tail call