2021-01-14 03:03:30 +00:00
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.ORG $C400
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Entry:
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BIT $FF58 ; well-known RTS location - where RTS is $60
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BVS PREntry ; always branches (used to relocatably branch)
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.ORG $C405
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INEntry:
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SEC
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BCC PREntry ; never happens, but has a magic ID byte @ C407 == 18
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CLV
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BVC PREntry ; always branches
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;; lookup table
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.ORG $C40B
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.byte $01 ; magic identifier
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.byte $20 ; magic identifier
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.byte .LOBYTE(ExitWithError)
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.byte .LOBYTE(ExitWithError)
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.byte .LOBYTE(ExitWithError)
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.byte .LOBYTE(ExitWithError)
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.byte $00
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.byte .LOBYTE(SetMouse)
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.byte .LOBYTE(ServeMouse)
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.byte .LOBYTE(ReadMouse)
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.byte .LOBYTE(ClearMouse)
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.byte .LOBYTE(PosMouse)
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.byte .LOBYTE(ClampMouse)
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.byte .LOBYTE(HomeMouse)
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.byte .LOBYTE(InitMouse)
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.byte .LOBYTE(ExitWithError)
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.byte .LOBYTE(ExitWithError)
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.byte .LOBYTE(ExitWithError)
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.byte .LOBYTE(ExitWithError)
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.byte .LOBYTE(ExitWithError)
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.byte .LOBYTE(ExitWithError)
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.ORG $C420
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PREntry:
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PHA ; save Y, X, A, S on the stack
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TYA
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PHA
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TXA
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PHA
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PHP
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SEI ; turn off interrupts while we find our address via the stack
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JSR $FF58 ; well-known RTS
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TSX ; grab stack pointer
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LDA $0100,X ; inspect the stack frame
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TAX ; now A and X hold the high byte of the return address to *us*
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ASL ; A <<= 4
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ASL
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ASL
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ASL
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TAY ; so Y = $n0, while X = $Cn for whatever slot we're in
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PLP ; pull Status off the stack
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BVC lastChance
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LDA $38 ; We're being invoked in an IN# context, not a PR# context.
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BNE PopAndReturn ; if $38/$39 don't point to us, then exit
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TXA
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EOR $39 ; is $39 == $Cn?
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BNE PopAndReturn
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InstallInHandler:
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LDA #$05 ; Update IN handler to point to $Cn05 instead of $Cn00, so we know we've
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STA $38 ;initialized it
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BNE INHandler
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lastChance:
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BCS INHandler
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PopAndReturn:
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PLA
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TAX
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PLA
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NOP
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PLA
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STA $c080,Y ; call soft-switch #0 for our slot to set mouse state
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RTS
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INHandler:
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STA $c081,Y ; call soft-switch #1 for our slot to fill the keyboard buffer w/ mouse info
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PLA
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LDA $0638,X ; pull the string length from this magic screen hole (X == $Cn)
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TAX ; which we'll return to the caller in X
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PLA ; restore Y
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TAY
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PLA ; restore A
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LDA $200,X ; Grab the last character entered in to the buffer by the magic switch call
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RTS
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SetMouse:
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2021-01-16 13:33:09 +00:00
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CMP #$10 ; values >= $10 are invalid
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2021-01-14 03:03:30 +00:00
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BCS ExitWithError
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STA $C0CF ; soft switch 0x0F, hard-coded slot 4 for now
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RTS
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ExitWithError:
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SEC ; the spec says carry is set on errors
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RTS
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ServeMouse:
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PHA
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SEI ; disable interrupts while we find out about interrupts
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STA $C0CE ; soft switch 0x0E, hard-coded slot 4 for now
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LDX #$04
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LDA $6B8,X ; check what interrupts we serviced
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AND #$0E
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BNE _sm1 ; if we serviced any, leave carry clear
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SEC ; ... but set carry if we serviced none
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_sm1:
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PLA
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RTS
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ReadMouse:
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STA $C0CB ; soft switch 0x0B, hard-coded slot 4 for now
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CLC
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RTS
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ClearMouse:
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STA $C0CA ; soft switch 0x0A, hard-coded slot 4 for now
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CLC
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RTS
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PosMouse:
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STA $C0C9 ; soft switch 0x09, hard-coded slot 4 for now
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CLC
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RTS
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ClampMouse:
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CMP #$02
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BCS ExitWithError
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STA $C0CD ; soft switch 0x0D, hard-coded slot 4 for now
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CLC
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RTS
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HomeMouse:
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STA $C0C8 ; soft switch 0x08, hard-coded slot 4 for now
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CLC
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RTS
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InitMouse:
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STA $C0CC ; soft switch 0x0C, hard-coded slot 4 for now
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CLC
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RTS
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.ORG $C4FB
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.byte $D6 ; magic identifier
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.ORG $C4FF
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.byte $01 ; version
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