Commodore CASSIOPEI, Руководство пользователя

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;Code relocater (this code can run from any address)
;===================================================
*=$1220
RELOCATE LDA $2C ;
CMP #$12 ;
BEQ RELOCATE_DONE ;code already at the correct location
;program_size = END_OF_PROGRAM - INIT
;first byte in memory = contents of $2C + low byte of label MAIN
;last byte in memory = first byte in program_sizeRELOCATE_REQ
LDA #<END_OF_PROGRAM
;store destination address in zero-page variable
STA DEST_ADR ;===============================================
LDA #>END_OF_PROGRAM ;
STA D1 ;high byte
LDA #<MAIN ;calculate first byte of code to be relocated in memory
STA SOURCE_ADR ;======================================================
LDA $2C ;
STA SOU1 ;high byte
;------------------------------------------------------------------------------
;ATTENTION: make sure that the option "calc address first then high/low byte"
;in CBM program studio is selected. Otherwise the lines below WILL fail!!!!!!!
;------------------------------------------------------------------------------
CLC ;add program size to get to the last byte
LDA SOURCE_ADR ;========================================
ADC #<END_OF_PROGRAM-MAIN ;carry that we be used in the next addition
STA SOURCE_ADR ;
LDA #>END_OF_PROGRAM-MAIN ;
ADC SOU1 ;add carry to high byte (if there was any)
STA SOU1 ;
CLV ;clear flag here to keep the loop fast
LDY #$00 ;clear reg here keeps the loop fast
RELOCATE_LP LDA (SOURCE_ADR),Y ;the actual moving of the program (the copy loop)
STA (DEST_ADR),Y ;================================================
LDA D1 ;check if last byte reached
CMP #>MAIN ;================================
BNE RELOCATE_00 ;
LDA DEST_ADR ;low byte of last written address
CMP #<MAIN ;
BEQ RELOCATE_DONE ;
RELOCATE_00 DEC SOURCE_ADR ;calculate next addresses
LDA SOURCE_ADR ;
CMP #$FF ;
BNE RELOCATE_01 ;========================
DEC SOU1 ;overflow detected
RELOCATE_01 DEC DEST_ADR ;decrement low-byte
LDA DEST_ADR ;
CMP #$FF ;
BNE RELOCATE_02 ;check for overflow of low byte
DEC D1 ;overflow detected, so we must also decrement high-byte
RELOCATE_02 ;CLV ;force conditional branch because
BVC RELOCATE_LP ;absolute jumps are impossible
RELOCATE_DONE JMP MAIN ;code is at correct location, so we may start it
;Main program (the code that will be relocated), it may not exceed $1DFF
;This means that your own program may be bigger then approximately 3Kbyte
;========================================================================
MAIN
;;;write your own program here;;;
END_OF_PROGRAM ;this label indicates the absolute end of the program
2019-10-27 Page 38 of 76 CASSIOPEI v2.0