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https://github.com/cc65/cc65.git
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156 lines
3.2 KiB
ArmAsm
156 lines
3.2 KiB
ArmAsm
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; ***
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; CC65 Lynx Library
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;
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; Originally by Bastian Schick
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; http://www.geocities.com/SiliconValley/Byte/4242/lynx/
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;
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; Ported to cc65 (http://www.cc65.org) by
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; Shawn Jefferson, June 2004
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;
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; ***
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;
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; void install_uploader(unsigned char divider);
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;
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; Installs an interrupt handler that hooks the comlynx rx/tx interrupts to
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; allow upload of code to the lynx from another computer via the comlynx
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; cable. divider values are in lynx.h
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;
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; Loader is installed under the mikey chip at $FE00.
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;
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.include "lynx.inc"
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.export _lynx_install_uploader
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.import _install_irq
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.import popa, pusha
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; ------------------------------------------------------------------------
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.segment "EXTZP": zeropage
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load_len: .res 2
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load_ptr: .res 2
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load_ptr2: .res 2
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.code
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; ------------------------------------------------------------------------
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; The following code will get moved to $FE00 when installing the uploader.
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.proc Loader
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.org $fe00
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run: ldy #4
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loop0: jsr read_byte
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sta load_len-1,y
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dey
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bne loop0 ; get destination and length
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tax ; lowbyte of length
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lda load_ptr
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sta load_ptr2
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lda load_ptr+1
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sta load_ptr2+1
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loop1: inx
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bne cont1
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inc load_len+1
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bne cont1
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jmp (load_ptr)
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cont1: jsr read_byte
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sta (load_ptr2),y
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sta PALETTE ; feedback ;-)
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iny
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bne loop1
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inc load_ptr2+1
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bra loop1
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read_byte:
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bit SERCTL
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bvc read_byte
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lda SERDAT
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rts
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.reloc
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.endproc
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; ------------------------------------------------------------------------
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.code
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_lynx_install_uploader:
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ldx #.sizeof(Loader)-1 ; put Loader in the right place
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loop: lda Loader,x ; x is length of loader
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sta Loader::run,x
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dex
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bpl loop
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;
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; install serial-irq vector
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;
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lda #4
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jsr pusha
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lda #<UpLoader
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ldx #>UpLoader
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jsr _install_irq ; set vector
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;
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; set baudrate
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;
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jsr popa ; get divider
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sta $fd10
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lda #%00011000 ; Baudrate = 1MHz/16/(divider+1)
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sta $fd11
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;
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; set ComLynx parameters
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;
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lda #%00011101 ; even par
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sta SERCTL ; set 8E1
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;
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; clear Rx-buffer
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;
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clear: bit SERCTL
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bvc ok0
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ldx SERDAT
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bra clear
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;
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; enable Rx-interrupt
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;
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ok0: ora #$40
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sta SERCTL
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rts
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; ------------------------------------------------------------------------
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; Rx-IRQ-handler
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UpLoader:
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lda SERDAT ; wait for the start sequence
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bit flag ; already seen $81 ?
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bpl again ; >= 0 => no
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cmp #$50 ; "P" ?
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bne again ; not correct, so clear flag
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jmp Loader::run
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again: stz flag
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cmp #$81
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bne exit
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sta flag
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;
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; last action : clear interrupt
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;
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exit: lda #$10
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sta INTRST
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rts
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.data
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flag: .byte 0
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