initial import, completely untested, does not compile yet

2014-11-29 14:18:48 +01:00
parent fed3179d3b
commit faccc5a3d6
23 changed files with 1974 additions and 0 deletions
--- a/libsrc/pcengine/psg.s
+++ b/libsrc/pcengine/psg.s
@@ -0,0 +1,29 @@
+                         
+						.include "pcengine.inc"
+
+            .export psg_init
+
+psg_init:
+                        clx
+                        stx     $0800   ; Select channel
+psg_clear_loop:
+                        stz     $0801   ; Clear global balance
+                        stz     $0802   ; Clear frequency LSB
+                        stz     $0803   ; Clear frequency MSB
+                        stz     $0804   ; Clear volume
+                        stz     $0805   ; Clear balance
+                        stz     $0807   ; Clear noise control
+                        stz     $0808   ; Clear LFO frequency
+                        stz     $0809   ; Clear LFO control
+
+                        cly
+psg_clear_waveform:     stz     $0806   ; Clear waveform byte
+                        iny
+                        cpy     #$20
+                        bne     psg_clear_waveform
+
+                        inx
+                        cpx     #$06
+                        bne     psg_clear_loop
+                        rts
+