mirror of
https://github.com/wwarthen/RomWBW.git
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49 lines
939 B
NASM
49 lines
939 B
NASM
;___MIO________________________________________________________________________________________________________________
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;
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; MEMORY MAPPED I/O
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;
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; PROVIDES AN INTERFACE TO BUFFER OUTPUT FROM PRE-INITIALIZATION
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; FUNCTIONS PRIOR TO OTHER OUTPUT METHODS BEING AVAILABLE
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;______________________________________________________________________________________________________________________
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;
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; $ CODE NOT STRICTLY REQUIRED.
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;
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MIOOUTPTR .EQU BNKTOP
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;
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MIO_INIT: ; MINIMAL INIT
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PUSH HL
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LD HL,MIOOUTPTR+2
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LD (MIOOUTPTR),HL
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LD (HL),'$'
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POP HL
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RET
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;
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MIO_OUTC: ; OUTPUT BYTE IN A
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PUSH HL
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PUSH DE
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LD HL,MIOOUTPTR
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LD E,(HL)
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INC HL
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LD D,(HL)
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LD H,D
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LD L,E
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LD (HL),A
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INC HL
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LD (MIOOUTPTR),HL
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LD (HL),'$'
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POP DE
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POP HL
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RET
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;
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; NOT USED AT THE MOMENT
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;
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MIO_INC: ; INPUT BYTE TO A
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LD A,'$'
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RET
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;
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;
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MIO_IST: ; INPUT STATUS TO A (NUM CHARS WAITING)
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LD A,1
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OR A
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RET ; DONE
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; |