pt3: add support for scaling the frequencies from 1.77MHz to 1MHz

The ZX Spectrum (default for pt3 files) runs the AY-3-8910 at 1.77MHz.

We do this by multiplying by 9/16 (which is a pain, but could be worse)

pt3_player/README.pt3_player

@@ -47,20 +47,27 @@ Using the PT3_PLAYER
 
 	The pt3_player.dsk should boot automatically.
 
-	Use the right/left arrow keys to switch songs.
+	Controls:
-	Press the space bar to pause playback.
+		Right/Left arrow	Switch songs
+		Spacebar		Pause playback.
+		M			Switch from 1MHz to 1.77MHz mode
 
 	FUTURE FEATURES:
 		Key to disable visualization
 		Key to skip ahead/back in pattern list
 		L to enable looping in the song
 
-Known Bugs:
+ZX Compatability:
-~~~~~~~~~~~
+~~~~~~~~~~~~~~~~~
-	Will try to display lowecase names on a II/II+
 
-	ZX Spectrum songs expect a 1.77MHz AY-3-8910, but
+	ZX Spectrum songs expect a 1.77MHz AY-3-8910, but the Apple II
-		the Apple II is 1MHz so song are higher(?) pitched
+		is 1MHz so by default songs would sound lower
+		pitched.  By default now we multiply by 9/16 to scale
+		things properly, but that does eat up extra CPU cycles.
+		You can toggle this on/off by pressing "M" when playing.
+
+	In theory we can create songs that expect 1MHz, but the pt3 format
+		has no way of indicating this.
 
 Adding other files
 ~~~~~~~~~~~~~~~~~~

pt3_player/interrupt_handler.s

@@ -189,7 +189,7 @@ check_keyboard:
 	beq	exit_interrupt
 
 	cmp	#(' '+$80)
-	bne	key_R
+	bne	key_M
 key_space:
 	lda	#$80
 	eor	DONE_PLAYING
@@ -207,13 +207,26 @@ lowbar:
 
 	jmp	quiet_exit
 
-key_R:
+key_M:
-	cmp	#'R'
+	cmp	#'M'
 	bne	key_left
 
-	lda	#$ff
+	lda	convert_177
-	eor	RASTERBARS_ON
+	eor	#$1
-	sta	RASTERBARS_ON
+	sta	convert_177
+	beq	at_1MHz
+
+	lda	#'7'+$80
+	sta	$7F4
+	sta	$BF4
+	jmp	done_key
+
+at_1MHz:
+	lda	#'0'+$80
+	sta	$7F4
+	sta	$BF4
+
+
 	jmp	done_key
 
 key_left:

pt3_player/pt3_lib.s

@@ -1803,16 +1803,128 @@ do_frame:
 	lda	note_a+NOTE_TONE_H	; Note A Period H
 	sta	REGISTER_DUMP+1		; into R1
 
+	lda	convert_177
+	beq	no_scale_a
+
+	; Convert from 1.77MHz to 1MHz by multiplying by 9/16
+
+	; first multiply by 8
+	asl	REGISTER_DUMP+0
+	rol	REGISTER_DUMP+1
+	asl	REGISTER_DUMP+0
+	rol	REGISTER_DUMP+1
+	asl	REGISTER_DUMP+0
+	rol	REGISTER_DUMP+1
+
+	; add in original to get 9
+	clc
+	lda	note_a+NOTE_TONE_L
+	adc	REGISTER_DUMP+0
+	sta	REGISTER_DUMP+0
+	lda	note_a+NOTE_TONE_H
+	adc	REGISTER_DUMP+1
+	sta	REGISTER_DUMP+1
+
+	; divide by 16 to get proper value
+	ror	REGISTER_DUMP+1
+	ror	REGISTER_DUMP+0
+	ror	REGISTER_DUMP+1
+	ror	REGISTER_DUMP+0
+	ror	REGISTER_DUMP+1
+	ror	REGISTER_DUMP+0
+	ror	REGISTER_DUMP+1
+	ror	REGISTER_DUMP+0
+	lda	REGISTER_DUMP+1
+	and	#$0f
+	sta	REGISTER_DUMP+1
+
+no_scale_a:
+
 	lda	note_b+NOTE_TONE_L	; Note B Period L
 	sta	REGISTER_DUMP+2		; into R2
 	lda	note_b+NOTE_TONE_H	; Note B Period H
 	sta	REGISTER_DUMP+3		; into R3
 
+	lda	convert_177
+	beq	no_scale_b
+
+	; Convert from 1.77MHz to 1MHz by multiplying by 9/16
+
+	; first multiply by 8
+	asl	REGISTER_DUMP+2
+	rol	REGISTER_DUMP+3
+	asl	REGISTER_DUMP+2
+	rol	REGISTER_DUMP+3
+	asl	REGISTER_DUMP+2
+	rol	REGISTER_DUMP+3
+
+	; add in original to get 9
+	clc
+	lda	note_b+NOTE_TONE_L
+	adc	REGISTER_DUMP+2
+	sta	REGISTER_DUMP+2
+	lda	note_b+NOTE_TONE_H
+	adc	REGISTER_DUMP+3
+	sta	REGISTER_DUMP+3
+
+	; divide by 16 to get proper value
+	ror	REGISTER_DUMP+3
+	ror	REGISTER_DUMP+2
+	ror	REGISTER_DUMP+3
+	ror	REGISTER_DUMP+2
+	ror	REGISTER_DUMP+3
+	ror	REGISTER_DUMP+2
+	ror	REGISTER_DUMP+3
+	ror	REGISTER_DUMP+2
+	lda	REGISTER_DUMP+3
+	and	#$0f
+	sta	REGISTER_DUMP+3
+
+no_scale_b:
+
 	lda	note_c+NOTE_TONE_L	; Note C Period L
 	sta	REGISTER_DUMP+4		; into R4
 	lda	note_c+NOTE_TONE_H	; Note C Period H
 	sta	REGISTER_DUMP+5		; into R5
 
+	lda	convert_177
+	beq	no_scale_c
+
+	; Convert from 1.77MHz to 1MHz by multiplying by 9/16
+
+	; first multiply by 8
+	asl	REGISTER_DUMP+4
+	rol	REGISTER_DUMP+5
+	asl	REGISTER_DUMP+4
+	rol	REGISTER_DUMP+5
+	asl	REGISTER_DUMP+4
+	rol	REGISTER_DUMP+5
+
+	; add in original to get 9
+	clc
+	lda	note_c+NOTE_TONE_L
+	adc	REGISTER_DUMP+4
+	sta	REGISTER_DUMP+4
+	lda	note_c+NOTE_TONE_H
+	adc	REGISTER_DUMP+5
+	sta	REGISTER_DUMP+5
+
+	; divide by 16 to get proper value
+	ror	REGISTER_DUMP+5
+	ror	REGISTER_DUMP+4
+	ror	REGISTER_DUMP+5
+	ror	REGISTER_DUMP+4
+	ror	REGISTER_DUMP+5
+	ror	REGISTER_DUMP+4
+	ror	REGISTER_DUMP+5
+	ror	REGISTER_DUMP+4
+	lda	REGISTER_DUMP+5
+	and	#$0f
+	sta	REGISTER_DUMP+5
+
+no_scale_c:
+
+
 	; Noise
 	; frame[6]= (pt3->noise_period+pt3->noise_add)&0x1f;
 	clc
@@ -1820,6 +1932,34 @@ do_frame:
 	adc	pt3_noise_add
 	and	#$1f
 	sta	REGISTER_DUMP+6
+	sta	temp_word_l
+
+	lda	convert_177
+	beq	no_scale_n
+
+	; Convert from 1.77MHz to 1MHz by multiplying by 9/16
+
+	; first multiply by 8
+	asl	REGISTER_DUMP+6
+	asl	REGISTER_DUMP+6
+	asl	REGISTER_DUMP+6
+
+	; add in original to get 9
+	clc
+	lda	temp_word_l
+	adc	REGISTER_DUMP+6
+
+	; divide by 16 to get proper value
+	ror	REGISTER_DUMP+6
+	ror	REGISTER_DUMP+6
+	ror	REGISTER_DUMP+6
+	ror	REGISTER_DUMP+6
+	lda	REGISTER_DUMP+6
+	and	#$1f
+	sta	REGISTER_DUMP+6
+
+no_scale_n:
+
 
 
 	; Mixer
@@ -1847,13 +1987,51 @@ do_frame:
 	clc
 	lda	pt3_envelope_slide_l
 	adc	temp_word_l
-;	sta	temp_word_l
+	sta	temp_word_l
 	sta	REGISTER_DUMP+11
 	lda	temp_word_h
 	adc	pt3_envelope_slide_h
-;	sta	temp_word_h
+	sta	temp_word_h
 	sta	REGISTER_DUMP+12
 
+	lda	convert_177
+	beq	no_scale_e
+
+	; Convert from 1.77MHz to 1MHz by multiplying by 9/16
+
+	; first multiply by 8
+	asl	REGISTER_DUMP+11
+	rol	REGISTER_DUMP+12
+	asl	REGISTER_DUMP+11
+	rol	REGISTER_DUMP+12
+	asl	REGISTER_DUMP+11
+	rol	REGISTER_DUMP+12
+
+	; add in original to get 9
+	clc
+	lda	temp_word_l
+	adc	REGISTER_DUMP+11
+	sta	REGISTER_DUMP+11
+	lda	temp_word_h
+	adc	REGISTER_DUMP+12
+	sta	REGISTER_DUMP+12
+
+	; divide by 16 to get proper value
+	ror	REGISTER_DUMP+12
+	ror	REGISTER_DUMP+11
+	ror	REGISTER_DUMP+12
+	ror	REGISTER_DUMP+11
+	ror	REGISTER_DUMP+12
+	ror	REGISTER_DUMP+11
+	ror	REGISTER_DUMP+12
+	ror	REGISTER_DUMP+11
+	lda	REGISTER_DUMP+12
+	and	#$0f
+	sta	REGISTER_DUMP+12
+
+no_scale_e:
+
+
 	; Envelope shape
 	lda	pt3_envelope_type
 	cmp	pt3_envelope_type_old

pt3_player/pt3_player.s

@@ -334,6 +334,20 @@ done_name_loop:
 	sta	CH
 	jsr     print_both_pages	; print, tail call
 
+	; update the MHz indicator with current state
+
+	lda	convert_177
+	beq	set_1MHz
+
+	lda	#'7'+$80
+	jmp     done_MHz
+
+set_1MHz:
+	lda     #'0'+$80
+done_MHz:
+        sta     $7F4
+        sta     $BF4
+
 	; Print Left Arrow (INVERSE)
 	lda	#'<'
 	sta	$6D0
@@ -592,5 +606,5 @@ found_message:		.asciiz "FOUND"
 ;done_message:		.asciiz "DONE PLAYING"
 loading_message:	.asciiz "LOADING"
 clock_string:		.asciiz "0:00 / 0:00"
-mhz_string:		.asciiz "1.0MHZ"
+mhz_string:		.asciiz "1.7MHZ"