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https://opencores.org/ocsvn/psg16/psg16/trunk
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robfinch |
AC97 EQU 0xFFFF_FFFF_FFDC_1000
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;--------------------------------------------------------------------------
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; Setup the AC97/LM4550 audio controller. Check keyboard for a CTRL-C
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; interrupt which may be necessary if the audio controller isn't
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; responding.
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;--------------------------------------------------------------------------
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;
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SetupAC97:
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subui sp,sp,#16
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sm [sp],r1/lr
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sac974:
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sc r0,AC97+0x26 ; trigger a read of register 26 (status reg)
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sac971: ; wait for status to register 0xF (all ready)
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call KeybdGetChar ; see if we needed to CTRL-C
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beqi r1,#CTRLC,sac973
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lc r1,AC97+0x68 ; wait for dirty bit to clear
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bne r1,r0,sac971
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lc r1,AC97+0x26 ; check status at reg h26, wait for
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andi r1,r1,#0x0F ; analogue to be ready
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bnei r1,#0x0F,sac974
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sac973:
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sc r0,AC97+2 ; master volume, 0db attenuation, mute off
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sc r0,AC97+4 ; headphone volume, 0db attenuation, mute off
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sc r0,AC97+0x18 ; PCM gain (mixer) mute off, no attenuation
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sc r0,AC97+0x0A ; mute PC beep
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setlo r1,#0x8000 ; bypass 3D sound
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sc r1,AC97+0x20
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sac972:
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call KeybdGetChar
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beqi r1,#CTRLC,sac975
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lc r1,AC97+0x68 ; wait for dirty bits to clear
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bne r1,r0,sac972 ; wait a while for the settings to take effect
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sac975:
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lm [sp],r1/lr
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addui sp,sp,#16
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ret
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