.MakeMusicOnTRI DEC pauseCountTRI ; Decrement the sound counter for TRI BEQ musr1 ; If the counter has reached zero, jump to musr1 to make ; music on the TRI channel RTS ; Otherwise return from the subroutine .musr1 LDA sectionDataTRI ; Set soundAddr(1 0) = sectionDataTRI(1 0) STA soundAddr ; LDA sectionDataTRI+1 ; So soundAddr(1 0) points to the note data for this STA soundAddr+1 ; part of the tune .musr2 LDY #0 ; Set Y to the next entry from the note data LDA (soundAddr),Y TAY INC soundAddr ; Increment soundAddr(1 0) to point to the next entry BNE musr3 ; in the note data INC soundAddr+1 .musr3 TYA ; Set A to the next entry that we just fetched from the ; note data BMI musr6 ; If bit 7 of A is set then this is a command byte, so ; jump to musr6 to process it CMP #$60 ; If the note data in A is less than $60, jump to musr4 BCC musr4 ADC #$A0 ; The note data in A is between $60 and $7F, so set the STA startPauseTRI ; following: ; ; startPauseTRI = A - $5F ; ; We know the C flag is set as we just passed through a ; BCC, so the ADC actually adds $A1, which is the same ; as subtracting $5F ; ; So this sets startPauseTRI to a value between 1 and ; 32, corresponding to note data values between $60 and ; $7F JMP musr2 ; Jump back to musr2 to move on to the next entry from ; the note data .musr4 ; If we get here then the note data in A is less than ; $60, which denotes a sound to send to the APU, so we ; now convert the data to a frequency and send it to the ; APU to make a sound on channel TRI CLC ; Set Y = (A + tuningAll + tuningTRI) * 2 ADC tuningAll CLC ADC tuningTRI ASL A TAY LDA noteFrequency,Y ; Set (A triLo) the frequency for note Y STA triLoCopy ; STA triLo ; Also save a copy of the low byte in triLoCopy LDA noteFrequency+1,Y LDX triLo ; Send (A triLo) to the APU via TRI_HI and TRI_LO STX TRI_LO STA TRI_HI STA triHi ; Set (triHi triLo) = (A triLo), though this value is ; never read again, so this has no effect LDA volumeEnvelopeTRI ; Set the counter to the volume change to the value of STA volumeCounterTRI ; volumeEnvelopeTRI, which gets set by the $F6 command LDA #%10000001 ; Configure the TRI channel as follows: STA TRI_LINEAR ; ; * Bit 7 set = reload the linear counter ; ; * Bits 0-6 = counter reload value of 1 ; ; So this enables a cycling triangle wave on the TRI ; channel (so the channel is enabled) .musr5 LDA soundAddr ; Set sectionDataTRI(1 0) = soundAddr(1 0) STA sectionDataTRI ; LDA soundAddr+1 ; This updates the pointer to the note data for the STA sectionDataTRI+1 ; channel, so the next time we can pick up where we left ; off LDA startPauseTRI ; Set pauseCountTRI = startPauseTRI STA pauseCountTRI ; ; So if startPauseTRI is non-zero (as set by note data ; the range $60 to $7F), the next startPauseTRI ; iterations of MakeMusicOnTRI will do nothing RTS ; Return from the subroutine .musr6 ; If we get here then bit 7 of the note data in A is ; set, so this is a command byte LDY #0 ; Set Y = 0, so we can use it in various commands below CMP #$FF ; If A is not $FF, jump to musr8 to check for the next BNE musr8 ; command ; If we get here then the command in A is $FF ; ; <$FF> moves to the next section in the current tune LDA nextSectionTRI ; Set soundAddr(1 0) to the following: CLC ; ADC sectionListTRI ; sectionListTRI(1 0) + nextSectionTRI(1 0) STA soundAddr ; LDA nextSectionTRI+1 ; So soundAddr(1 0) points to the address of the next ADC sectionListTRI+1 ; section in the current tune STA soundAddr+1 ; ; So if we are playing tune 2 and nextSectionTRI(1 0) ; points to the second section, then soundAddr(1 0) ; will now point to the second address in tune2Data_TRI, ; which itself points to the note data for the second ; section at tune2Data_TRI_1 LDA nextSectionTRI ; Set nextSectionTRI(1 0) = nextSectionTRI(1 0) + 2 ADC #2 ; STA nextSectionTRI ; So nextSectionTRI(1 0) now points to the next section, TYA ; as each section consists of two bytes in the table at ADC nextSectionTRI+1 ; sectionListTRI(1 0) STA nextSectionTRI+1 LDA (soundAddr),Y ; If the address at soundAddr(1 0) is non-zero then it INY ; contains a valid address to the section's note data, ORA (soundAddr),Y ; so jump to musr7 to skip the following BNE musr7 ; ; This also increments the index in Y to 1 ; If we get here then the command is trying to move to ; the next section, but that section contains value of ; $0000 in the tuneData table, so there is no next ; section and we have reached the end of the tune, so ; instead we jump back to the start of the tune LDA sectionListTRI ; Set soundAddr(1 0) = sectionListTRI(1 0) STA soundAddr ; LDA sectionListTRI+1 ; So we start again by pointing soundAddr(1 0) to the STA soundAddr+1 ; first entry in the section list for channel TRI, which ; contains the address of the first section's note data LDA #2 ; Set nextSectionTRI(1 0) = 2 STA nextSectionTRI ; LDA #0 ; So the next section after we play the first section STA nextSectionTRI+1 ; will be the second section .musr7 ; By this point, Y has been incremented to 1 LDA (soundAddr),Y ; Set soundAddr(1 0) to the address at soundAddr(1 0) TAX ; DEY ; As we pointed soundAddr(1 0) to the address of the LDA (soundAddr),Y ; new section above, this fetches the first address from STA soundAddr ; the new section's address list, which points to the STX soundAddr+1 ; new section's note data ; ; So soundAddr(1 0) now points to the note data for the ; new section, so we're ready to start processing notes ; and commands when we rejoin the musr2 loop JMP musr2 ; Jump back to musr2 to start processing data from the ; new section .musr8 CMP #$F6 ; If A is not $F6, jump to musr10 to check for the next BNE musr10 ; command ; If we get here then the command in A is $F6 ; ; <$F6 $xx> sets the volume envelope counter to $xx ; ; In the other channels, this command lets us choose a ; volume envelope number ; ; In the case of the TRI channel, there isn't a volume ; envelope as such, because the channel is either off or ; on and doesn't have a volume setting, so instead of ; this command choosing a volume envelope number, it ; sets a counter that determines the number of ; iterations before the channel gets silenced ; ; I've kept the variable names in the same format as the ; other channels for consistency LDA (soundAddr),Y ; Fetch the next entry in the note data into A INC soundAddr ; Increment soundAddr(1 0) to point to the next entry BNE musr9 ; in the note data INC soundAddr+1 .musr9 STA volumeEnvelopeTRI ; Set volumeEnvelopeTRI to the volume envelope number ; that we just fetched JMP musr2 ; Jump back to musr2 to move on to the next entry from ; the note data .musr10 CMP #$F7 ; If A is not $F7, jump to musr12 to check for the next BNE musr12 ; command ; If we get here then the command in A is $F7 ; ; <$F7 $xx> sets the pitch envelope number to $xx LDA (soundAddr),Y ; Fetch the next entry in the note data into A INC soundAddr ; Increment soundAddr(1 0) to point to the next entry BNE musr11 ; in the note data INC soundAddr+1 .musr11 STA pitchEnvelopeTRI ; Set pitchEnvelopeTRI to the pitch envelope number that ; we just fetched STY pitchIndexTRI ; Set pitchIndexTRI = 0 to point to the start of the ; data for pitch envelope A JMP musr2 ; Jump back to musr2 to move on to the next entry from ; the note data .musr12 CMP #$F8 ; If A is not $F8, jump to musr13 to check for the next BNE musr13 ; command ; If we get here then the command in A is $F8 ; ; <$F8> sets the volume of the TRI channel to zero LDA #1 ; Set the counter in volumeCounterTRI to 1, so when we STA volumeCounterTRI ; return from the subroutine and call ApplyEnvelopeTRI, ; the TRI channel gets silenced JMP musr5 ; Jump to musr5 to return from the subroutine, so we ; continue on from the next entry from the note data in ; the next iteration .musr13 CMP #$F9 ; If A is not $F9, jump to musr14 to check for the next BNE musr14 ; command ; If we get here then the command in A is $F9 ; ; <$F9> enables the volume envelope for the TRI channel JMP musr5 ; Jump to musr5 to return from the subroutine, so we ; continue on from the next entry from the note data in ; the next iteration .musr14 CMP #$FB ; If A is not $FB, jump to musr16 to check for the next BNE musr16 ; command ; If we get here then the command in A is $FB ; ; <$FB $xx> sets the tuning for all channels to $xx LDA (soundAddr),Y ; Fetch the next entry in the note data into A INC soundAddr ; Increment soundAddr(1 0) to point to the next entry BNE musr15 ; in the note data INC soundAddr+1 .musr15 STA tuningAll ; Store the entry we just fetched in tuningAll, which ; sets the tuning for the TRI, TRI and TRI channels (so ; this value gets added to every note on those channels) JMP musr2 ; Jump back to musr2 to move on to the next entry from ; the note data .musr16 CMP #$FC ; If A is not $FC, jump to musr18 to check for the next BNE musr18 ; command ; If we get here then the command in A is $FC ; ; <$FC $xx> sets the tuning for the TRI channel to $xx LDA (soundAddr),Y ; Fetch the next entry in the note data into A INC soundAddr ; Increment soundAddr(1 0) to point to the next entry BNE musr17 ; in the note data INC soundAddr+1 .musr17 STA tuningTRI ; Store the entry we just fetched in tuningTRI, which ; sets the tuning for the TRI channel (so this value ; gets added to every note on those channels) JMP musr2 ; Jump back to musr2 to move on to the next entry from ; the note data .musr18 CMP #$F5 ; If A is not $F5, jump to musr19 to check for the next BNE musr19 ; command ; If we get here then the command in A is $F5 ; ; <$F5 $xx &yy> changes tune to the tune data at &yyxx ; ; It does this by setting sectionListTRI(1 0) to &yyxx ; and soundAddr(1 0) to the address stored in &yyxx ; ; To see why this works, consider switching to tune 2, ; for which we would use this command: ; ; <$F5 LO(tune2Data_TRI) LO(tune2Data_TRI)> ; ; This sets: ; ; sectionListTRI(1 0) = tune2Data_TRI ; ; so from now on we fetch the addresses for each section ; of the tune from the table at tune2Data_TRI ; ; It also sets soundAddr(1 0) to the address in the ; first two bytes of tune2Data_TRI, to give: ; ; soundAddr(1 0) = tune2Data_TRI_0 ; ; So from this point on, note data is fetched from the ; table at tune2Data_TRI_0, which contains notes and ; commands for the first section of tune 2 LDA (soundAddr),Y ; Fetch the next entry in the note data into A TAX ; Set sectionListTRI(1 0) = &yyxx STA sectionListTRI ; INY ; Also set soundAddr(1 0) to &yyxx and increment the LDA (soundAddr),Y ; index in Y to 1, both of which we use below STX soundAddr STA soundAddr+1 STA sectionListTRI+1 LDA #2 ; Set nextSectionTRI(1 0) = 2 STA nextSectionTRI ; DEY ; So the next section after we play the first section STY nextSectionTRI+1 ; of the new tune will be the second section ; ; Also decrement the index in Y back to 0 LDA (soundAddr),Y ; Set soundAddr(1 0) to the address stored at &yyxx TAX INY LDA (soundAddr),Y STA soundAddr+1 STX soundAddr JMP musr2 ; Jump back to musr2 to move on to the next entry from ; the note data .musr19 CMP #$F4 ; If A is not $F4, jump to musr21 to check for the next BNE musr21 ; command ; If we get here then the command in A is $F4 ; ; <$F4 $xx> sets the playback speed to $xx LDA (soundAddr),Y ; Fetch the next entry in the note data into A, which ; contains the new speed INC soundAddr ; Increment soundAddr(1 0) to point to the next entry BNE musr20 ; in the note data INC soundAddr+1 .musr20 STA tuneSpeed ; Set tuneSpeed and tuneSpeedCopy to A, to change the STA tuneSpeedCopy ; speed of the current tune to the specified speed JMP musr2 ; Jump back to musr2 to move on to the next entry from ; the note data .musr21 CMP #$FE ; If A is not $FE, jump to musr22 to check for the next BNE musr22 ; command ; If we get here then the command in A is $FE ; ; <$FE> stops the music and disables sound STY playMusic ; Set playMusic = 0 to stop playing the current tune, so ; only a new call to ChooseMusic will start the music ; again PLA ; Pull the return address from the stack, so the RTS PLA ; instruction at the end of StopSounds actually returns ; from the subroutine that called MakeMusic, so we stop ; the music and return to the MakeSounds routine (which ; is the only routine that calls MakeMusic) JMP StopSoundsS ; Jump to StopSounds via StopSoundsS to stop the music ; and return to the MakeSounds routine .musr22 BEQ musr22 ; If we get here then bit 7 of A was set but the value ; didn't match any of the checks above, so this ; instruction does nothing and we fall through into ; ApplyEnvelopeTRI, ignoring the data in A ; ; I'm not sure why the instruction here is an infinite ; loop, but luckily it isn't triggered as A is never ; zero at this pointName: MakeMusicOnTRI [Show more] Type: Subroutine Category: Sound Summary: Play the current music on the TRI channel Deep dive: Music in NES EliteContext: See this subroutine in context in the source code References: This subroutine is called as follows: * MakeMusic calls MakeMusicOnTRI
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Subroutine StopSoundsS (category: Sound)
A jump table entry at the start of bank 6 for the StopSounds routine
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Configuration variable TRI_HI = $400B
The APU period register (high byte) for the triangle wave channel
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Configuration variable TRI_LINEAR = $4008
The APU linear counter register for the triangle wave channel
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Configuration variable TRI_LO = $400A
The APU period register (low byte) for the triangle wave channel
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Label musr1 is local to this routine
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Label musr10 is local to this routine
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Label musr11 is local to this routine
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Label musr12 is local to this routine
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Label musr13 is local to this routine
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Label musr14 is local to this routine
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Label musr15 is local to this routine
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Label musr16 is local to this routine
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Label musr17 is local to this routine
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Label musr18 is local to this routine
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Label musr19 is local to this routine
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Label musr2 is local to this routine
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Label musr20 is local to this routine
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Label musr21 is local to this routine
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Label musr22 is local to this routine
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Label musr3 is local to this routine
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Label musr4 is local to this routine
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Label musr5 is local to this routine
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Label musr6 is local to this routine
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Label musr7 is local to this routine
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Label musr8 is local to this routine
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Label musr9 is local to this routine
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Variable nextSectionTRI in workspace WP
The next section for the TRI channel of the current tune
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Variable noteFrequency (category: Sound)
A table of note frequencies
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Variable pauseCountTRI in workspace WP
Pause for this many iterations before continuing to process note data on channel TRI, decrementing the value for each paused iteration
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Variable pitchEnvelopeTRI in workspace WP
The number of the pitch envelope to be applied to the current tune on channel TRI
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Variable pitchIndexTRI in workspace WP
The index of the entry within the pitch envelope to be applied to the current tune on channel TRI
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Variable sectionDataTRI in workspace WP
The address of the note data for channel TRI of the the current section of the current tune
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Variable sectionListTRI in workspace WP
The address of the section list for channel TRI of the current tune
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Variable startPauseTRI in workspace WP
Pause for this many iterations before starting to process each batch of note data on channel TRI
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Variable tuneSpeedCopy in workspace WP
The starting speed of the current tune, as stored in the tune's data
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Variable volumeCounterTRI in workspace WP
A counter for keeping track of repeated bytes from the volume envelope on channel TRI
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Variable volumeEnvelopeTRI in workspace WP
The number of the volume envelope to be applied to the current tune on channel TRI