Snippet:Playsong - Revision history

E5frog at 11:48, 5 February 2020

2020-02-05T11:48:37Z

E5frog at 11:59, 11 November 2013

2013-11-11T11:59:38Z

E5frog at 15:11, 9 November 2013

2013-11-09T15:11:41Z

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E5frog: 1 revision

2012-11-16T21:23:46Z

1 revision

Admin at 03:23, 25 November 2004

2004-11-25T03:23:11Z

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This code is taken from [[Cartridge:Pro_Football|cart #24]]. It plays a song from memory using the address stored in [[Data counter|DC0]]. It starts a loop through the data, taking two bytes at a time; the first is the duration of the note, and the second is the frequency. It outputs it through the [[port]]s, delays, and takes another two bytes. If it finds the duration byte is equal to 0, it exits, so a 0 byte marks the end of a song. If it finds the frequency byte is 255, it instead generates a pause for the specified duration. (note: using a frequency of 254 ''or'' 255 otherwise outputs the same note) The pausing functionality isn't in the original disassembly, but was added afterwards.

<pre>
;-----------;
; Play Song ;
;-----------;

; plays a song from memory
; song address stored in DC0
; uses r3, r4, r5, r7

playSong: ; taken from Pro Football
lis 3 ; A = 3
lr 4, A ; A -> r4, r4 = 3

.playSongDelay1:
inc ; increase A
bnz .playSongDelay1 ; [Branch if not zero] back to .psdly1
am ; Memory adressed by DC0 is added to A, flags set - get duration data
lr 7, A ; A -> r7
bz .playSongEnd ; Go to end if zero
lm ; Load memory into A (adressed by DC0) - get frequency data
lr 5, A ; A -> r5

; check to see if we should pause
inc
bnc .playSongLoop ; it didn't roll over, play a note instead

.playSongPause:
li $ff
lr 6, A
.playSongPauseLoop:
ds 6 ; pause counter
bnz .playSongPauseLoop
ds 7 ; duration of the pause
bnz .playSongPause

; play the next note
br playSong

.playSongLoop:
li $80 ; A= $80
outs 5 ; Send A -> port 5
lr A, 5 ; r5 -> A

.playSongDelay2:
inc ; increase A
bnz .playSongDelay2 ; [Branch if not zero] back to .psdly2
outs 5 ; A -> port 5
lr A, 5 ; r5 -> A

.playSongDelay3:
inc ; increase A
bnz .playSongDelay3 ; [Branch if not zero] back to .psdly3
ds 4 ; decrease r4
bnz .playSongLoop ; [Branch if not zero] back to .psloop
lis 3 ; A = 3
lr 4, A ; A -> r4
ds 7 ; decrease r7
bnz .playSongLoop ; [Branch if not zero] back to .psloop
br playSong ; start over - branch to beginning

.playSongEnd:
pop ; return from the subroutine

</pre>

== See Also ==
* [[Snippet:Music_60.h|Music_60.h]] - Contains the correct frequency and duration for notes ranging from G3-G5 in the form of [[DASM]] [[macro]]s, to make song writing easier.

← Older revision		Revision as of 11:48, 5 February 2020
Line 1:		Line 1:
−	This code is taken from [[~~Cartridge~~:~~Pro_Football~~\|cart #24]]. It plays a song from memory using the address stored in [[Data counter\|DC0]]. It starts a loop through the data, taking two bytes at a time; the first is the duration of the note, and the second is the frequency. It outputs it through the [[port]]s, delays, and takes another two bytes. If it finds the duration byte is equal to 0, it exits, so a 0 byte marks the end of a song. If it finds the frequency byte is 255, it instead generates a pause for the specified duration. (note: using a frequency of 254 ''or'' 255 otherwise outputs the same note) The pausing functionality isn't in the original disassembly, but was added afterwards.	+	This code is taken from [[Disassembly:Videocart_24\|cart #24]]. It plays a song from memory using the address stored in [[Data counter\|DC0]]. It starts a loop through the data, taking two bytes at a time; the first is the duration of the note, and the second is the frequency. It outputs it through the [[port]]s, delays, and takes another two bytes. If it finds the duration byte is equal to 0, it exits, so a 0 byte marks the end of a song. If it finds the frequency byte is 255, it instead generates a pause for the specified duration. (note: using a frequency of 254 ''or'' 255 otherwise outputs the same note) The pausing functionality isn't in the original disassembly, but was added afterwards.

	Second version has some edits and additions B00daW from his Sleizsa-package v.0.3.		Second version has some edits and additions B00daW from his Sleizsa-package v.0.3.

@@ Line 1: / Line 1: @@
 This code is taken from [[Cartridge:Pro_Football|cart #24]]. It plays a song from memory using the address stored in [[Data counter|DC0]]. It starts a loop through the data, taking two bytes at a time; the first is the duration of the note, and the second is the frequency. It outputs it through the [[port]]s, delays, and takes another two bytes. If it finds the duration byte is equal to 0, it exits, so a 0 byte marks the end of a song. If it finds the frequency byte is 255, it instead generates a pause for the specified duration. (note: using a frequency of 254 ''or'' 255 otherwise outputs the same note) The pausing functionality isn't in the original disassembly, but was added afterwards.
 <pre>
@@ Line 65: / Line 67: @@
 </pre>
 == How does it sound? ==

← Older revision	Revision as of 21:23, 16 November 2012
(No difference)