Skip to navigation

⌂ ∞ ▽ Elite on the 6502

Keyboard: ZEKTRAN

[Commodore 64 version]

       Name: ZEKTRAN                                                 [Show more]
       Type: Subroutine
   Category: Keyboard
    Summary: Clear the key logger

    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * BR1 (Part 1 of 2) calls ZEKTRAN
             * RDKEY calls ZEKTRAN
             * TITLE calls ZEKTRAN




.ZEKTRAN

 LDX #64                ; We want to clear the 65 key logger locations from
                        ; KEYLOOK to KEYLOOK+64, so set a counter in X

 LDA #0                 ; We want to zero the key logger buffer, so set A % 0

 STA thiskey            ; Reset the value of thiskey in the key logger, which
                        ; is used for logging keys that don't appear in the
                        ; keyboard table

.ZEKLOOP

 STA KEYLOOK,X          ; Reset the X-th byte of the key logger buffer to 0

 DEX                    ; Decrement the loop counter

 BPL ZEKLOOP            ; Loop back until we have zeroed bytes #11 through #0

 RTS                    ; Return from the subroutine

 RTS                    ; This instruction has no effect as we already returned
                        ; from the subroutine