104 lines
3.3 KiB
NASM
104 lines
3.3 KiB
NASM
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; ----------------- assembly instructions ----------------------------
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;
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; this is a subroutine library only
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; it must be included in an executable source file
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;
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;
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;*** I/O Locations *******************************
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; define the i/o address of the ACIA1 chip
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;*** 6551 CIA ************************
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UCSR0A = $3fc0
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UCSR0B = $3fc1
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UCSR0C = $3fc2
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UDR0 = $3fc6
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;
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;***********************************************************************
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; 6551 I/O Support Routines
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;
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ACIA1_init LDX #<ACIA1_Input ; set up RAM vectors for
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LDA #>ACIA1_Input ; Input, Output, and Scan
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TAY ; Routines
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EOR #$A5 ;
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sta ChrInVect+2 ;
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sty ChrInVect+1 ;
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stx ChrInVect ;
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LDX #<ACIA1_Scan ;
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LDA #>ACIA1_Scan ;
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TAY ;
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EOR #$A5 ;
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sta ScanInVect+2 ;
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sty ScanInVect+1 ;
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stx ScanInVect ;
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LDX #<ACIA1_Output ;
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LDA #>ACIA1_Output ;
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TAY ;
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EOR #$A5 ;
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sta ChrOutVect+2 ;
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sty ChrOutVect+1 ;
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stx ChrOutVect ;
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lda #<ACIA1_scan ; setup BASIC vectors
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sta VEC_IN
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lda #>ACIA1_scan ; BASIC's chr input
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sta VEC_IN+1
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lda #<ACIA1_Output
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sta VEC_OUT
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lda #>ACIA1_Output ; BASIC's chr output
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sta VEC_OUT+1
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lda #<Psave
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sta VEC_SV
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lda #>Psave ; SAVE cmd
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sta VEC_SV+1
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lda #<pload
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sta VEC_LD
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lda #>pload ; LOAD cmd
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sta VEC_LD+1
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rts ; done
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;
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; input chr from ACIA1 (waiting)
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;
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cin
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ACIA1_Input
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lda UCSR0A ; Serial port status
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and #$80 ; RXC0 bit
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beq ACIA1_Input ; no char to get
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lda UDR0 ; get chr
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RTS ;
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;
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; non-waiting get character routine
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;
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CSCAN
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ACIA1_Scan clc
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lda UCSR0A ; Serial port status
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and #$80 ; RXC0 bit
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beq ACIA1_scan2
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lda UDR0 ; get chr
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sec
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ACIA1_scan2 rts
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;
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; output to OutPut Port
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;
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cout
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ACIA1_Output PHA ; save registers
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ACIA1_Out1 lda UCSR0A ; Serial port status
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and #$20 ; UDRE0 bit
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beq ACIA1_Out1 ; no
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PLA ; get chr
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sta UDR0 ; put character to Port
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RTS ; done
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CROUT lda #$0d
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jsr cout
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lda #$0a
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bra cout
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cbrk jsr cscan
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bcc cbrk2
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cmp #$03
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beq cbrk2
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clc
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cbrk2 rts
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;
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;end of file
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