46 lines
1.8 KiB
NASM
46 lines
1.8 KiB
NASM
; printstring.asm
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;
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; This is a simple demonstration routine for the emulator to take a null terminated string from RAM
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; and display it out to the emulators text printer.
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; The routine takes a simple argument on the stack with the address of the string.
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; The routine will use the DISPLAY variable set in .data
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;
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; Version: 0.2.1
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GLOBAL START
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GLOBAL PRINTSTRING
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SECTION .text
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START: LDAB MYSTRING ; Put string address into AB
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PHAB ; and push to the stack
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JSR PRINTSTRING ; Call PRINTSTRING routine
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SECTION .printstring
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PRINTSTRING: PLAB
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PHAB ; Get the address of the string
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LDA $DISPLAY ; Set the output address
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PHA
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LDAB $DISPLAY+1 ; Set the output address
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PHAB
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PRINTLOOP: LDAB CD
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CMP A,B
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BEQ RETURN ; If we pull a 0, or null then we are done
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STAL [SP]
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ADD C,$1 ; Increment our string location by 1
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BCS ROLLOVER ; If it rolls over we need to go handle high byte
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PLAB
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ADD A,$1 ; Icrement our output by 1
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PHAB
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JMP PRINTLOOP ; Loop back and keep reading in the string
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ROLLOVER: ADD D, $1
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PLAB
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ADD B, $1
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PHAB
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JMP PRINTLOOP ; Loop back and keep reading in the string
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RETURN: PLAB ; To return we need to clean up our stack use first
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PLA
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RTS
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SECTION .data
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DISPLAY equ D00000h
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MYSTRING DB "Welcome to the MatCat 8SA1 Computer Simulator!\n\nThis is a full hardware simulation of the computer to allow for easy development testing. It is currently a heavy work in progress as it is very early alpha, so check back often for new features!\n\n\nThis demo can be seen in the examples folder on the git page at: \nhttps://mygit.space/MatCat.OpenSource/8SA1Sim", 0 |