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60 lines
1.9 KiB
ArmAsm
60 lines
1.9 KiB
ArmAsm
; http://macgui.com/usenet/?group=2&id=8366
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; Mockingboad programming:
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; + Has two 6522 I/O chips
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; + Often in slot 4
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; $C400 ORB1 function to perform, OUT 1
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; $C401 ORA1 data, OUT 1
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; $C402 DDRB1 data direction, OUT 1
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; $C403 DDRA1 data direction, OUT 1
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; $C480 ORB2 function to perform, OUT 2
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; $C481 ORA2 data, OUT 2
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; $C482 DDRB2 data direction, OUT 2
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; $C483 DDRA2 data direction, OUT 2
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; To Initialize the 6522s: Store $FF at the DDRxx addresses
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; Your program gets access to a PSG via the 6522 by using a few basic
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; Function codes which set the PSG's I/O control lines:
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;
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; Set Inactive = $04 Set PSG Reg# = $07 Write Data = $06 Reset = $00
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;
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; To Write to a PSG register: Tell the PSG which Register you wish to access
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; (i.e. Set the "current register" #) and Write the data. This is easiest to
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; do with subroutines to handle the basic Functions.
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;
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; Example Subroutines (for Output Channel 1):
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;
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; Set Reg # 1000: A9 07 8D 00 C4 A9 04 8D 00 C4 60
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; Write Data 100B: A9 06 8D 00 C4 A9 04 8D 00 C4 60
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; Notice that each Function sub ends by setting the PSG control lines to
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; Inactive.
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; Similarly, to do a Reset (set all PSG regs to zero) ...
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; Reset 1016: A9 00 8D 00 C4 A9 04 8D 00 C4 60
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; To put the value $55 in PSG Register 02 (Channel B Freq. fine) ....
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; 1080: A9 02 put Reg# in A
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; 1082: 8D 01 C4 store A at the Data address ORA1
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; 1085: 20 00 10 JSR to Set Reg# (sets "current register" to Register
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; 2)
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; 1088: A9 55 put the value $55 in A
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; 108A: 8D 01 C4 store A at the Data address ORA1
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; 108D: 20 0B 10 JSR to Write Data ($55 goes into PSG Register 2)
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; 1090: 60 Exit from subroutine
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.include "zp.inc"
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;=============================
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; set low-res graphics, page 0
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;=============================
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jsr HOME
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jsr TEXT
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forever_loop:
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jmp forever_loop
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