101 lines
4.2 KiB
NASM
101 lines
4.2 KiB
NASM
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; ----------------- assembly instructions ----------------------------
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;
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;****************************************************************************
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; Reset, Interrupt, & Break Handlers
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;****************************************************************************
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*= $FF00 ; put this in last page of ROM
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;--------------Reset handler----------------------------------------------
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Reset SEI ; diable interupts
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CLD ; clear decimal mode
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LDX #$FF ;
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TXS ; init stack pointer
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;
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; you can patch in a test for keypress here to bypass memory erase.
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; It will then test the vectors, and jump to your routine.
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;
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Set_Vectors LDX #<Start_OS ; *** only outside reference in reset routine
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LDA #>Start_OS ; *** points to Monitor Boot routine
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sta RESvector+1 ;
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stx RESvector ;
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LDX #<INTret ; set up to point to RTI command
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LDA #>INTret ; (no system NMI applications)
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sta NMIvector+1 ;
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stx NMIvector ;
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LDX #<INTret ; set up to point to RTI command
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LDA #>INTret ; (no system INT applications)
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sta INTvector+1 ;
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stx INTvector ;
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LDX #<BRKroutine ; set up to point to my BRK routine
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LDA #>BRKroutine ;
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sta BRKvector+1 ;
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stx BRKvector ;
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lda #<ACIA1_Scan
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sta VEC_IN
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lda #>ACIA1_Scan
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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
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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
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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
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sta VEC_LD+1
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;
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; select the IO device driver here
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;
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jsr ACIA1_init ; init the I/O devices
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Clr_regs lda #$00 ; Clear registers
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TAY ;
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TAX ;
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CLC ; clear flags
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CLD ; clear decimal mode
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CLI ; Enable interrupt system
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JMP (RESvector) ; Monitor for cold reset
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;
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NMIjump jmp (NMIvector) ;
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INTret RTI ; Null Interrupt return
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Interrupt PHX ;
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PHA ;
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TSX ; get stack pointer
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LDA $0103,X ; load INT-P Reg off stack
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AND #$10 ; mask BRK
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BNE BrkCmd ; BRK CMD
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PLA ;
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PLX ;
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jmp (INTvector) ; let user routine have it
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BrkCmd pla ;
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plx ;
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jmp (BRKvector) ; patch in user BRK routine
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RRTS rts ; documented RTS instruction
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;
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;
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;
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; *** VERSION Notes ***
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; 3.5 added the text dump command, 'q'
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; 4.0 reorganized structure, added RAM vectors for chrin, scan_in, and chrout
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; 4.1 fixed set time routine so 20-23 is correct
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; 4.2 RST, IRQ, NMI, BRK all jmp ind to 02xx page to allow user prog to control
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; 4.3 added status register bits to printreg routine
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; 4.4 refined set time to reduce unneeded sec's and branches, disp time added CR,
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; and added zeromem to the reset routine, ensuring a reset starts fresh every time!
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; continued to re-organize - moved monitor's brk handler into mon area.
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; 65C02 Firmware Notes
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;
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; NMIjmp = $FFFA
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; RESjmp = $FFFC
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; INTjmp = $FFFE
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*= $FFFA
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.word NMIjump
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.word Reset
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.word Interrupt
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;end of file
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