mirror of https://github.com/stid/woz64.git
45 lines
2.4 KiB
NASM
45 lines
2.4 KiB
NASM
#importonce
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.filenamespace MC6502
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https://sta.c64.org/cbm64mem.html
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// ========================================================
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// ////// CONSTANTS ///////////////////////////////////////
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// ========================================================
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.label ZR0 = $0 // Processor port data direction register. Bits:
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// Bit #x: 0 = Bit #x in processor port can only be read; 1 = Bit #x in processor port can be read and written.
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// Default: $2F, %00101111.
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.label ZR1 = $1 // Processor port. Bits:
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// Bits #0-#2: Configuration for memory areas $A000-$BFFF, $D000-$DFFF and $E000-$FFFF. Values:
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// %x00: RAM visible in all three areas.
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// %x01: RAM visible at $A000-$BFFF and $E000-$FFFF.
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// %x10: RAM visible at $A000-$BFFF; KERNAL ROM visible at $E000-$FFFF.
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// %x11: BASIC ROM visible at $A000-$BFFF; KERNAL ROM visible at $E000-$FFFF.
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// %0xx: Character ROM visible at $D000-$DFFF. (Except for the value %000, see above.)
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// %1xx: I/O area visible at $D000-$DFFF. (Except for the value %100, see above.)
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// Bit #3: Datasette output signal level.
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// Bit #4: Datasette button status; 0 = One or more of PLAY, RECORD, F.FWD or REW pressed; 1 = No button is pressed.
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// Bit #5: Datasette motor control; 0 = On; 1 = Off.
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// Default: $37, %00110111.
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// ========================================================
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// ////// METHODS /////////////////////////////////////////
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// ========================================================
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* = * "mc6502 HW"
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init: {
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// SET UP THE 6510 LINES
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lda #%00110111 // MOTOR OFF, HIRAM LOWRAM CHAREN HIGH
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sta MC6502.ZR1 // set 1110 0111, motor off, enable I/O, enable KERNAL, Enable BASIC
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lda #%00101111 // set 0010 1111, 0 = input, 1 = output
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sta MC6502.ZR0 // save the 6510 I/O port direction register
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rts
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}
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