************************************** * This is a music player for Ed Snider's CoCo PSG Cartridge for the Tandy Color Computer * The YM2149 sound chip is a clone of the AY-3-8910 Sound chip with a few differences * ************************************** * CoCoPSG background Player for BASIC Version 1.00 - By Glen Hewlett * Do whatever you want with this code... Have fun! * * Playback of notes and velocity info on the CoCoPSG is done by sending the note and velocity data to the CoCo PSG. * The data file includes a counter that is the number of every two vsync's which is 30 times a second in NTSC * The player then counts down until the number reaches zero then the new notes or velocity info is sent to the CoCo PSG, etc. * This means the player uses very little CPU cycles as a background process since it only reads the data and sends it to the * CoCo PSG when the note or velocity change is needed and this countdown is done every 2nd vsync. * * 5 Byte header: * Byte Value * 00-02 'PSG' - Header Identifier * 03 $xx - File version # currently only supprts a value of $01 for version 1.00 * 04 $xx - Number of times to loop this song where xx is: * $00 - Don't change the number of loops value * $01 to $FE - loop this number of times * $FF - loop forever * All bytes at this point are data bytes that are encoded as per the info below. * * First the descriptor byte * Left nibble = # of vsyncs/2 to count until next change in tone or velocity is done * $0x to $Fx = 0 to 15 delay count before next note or velocity change, add one to get real value of 1 to 16 * * Right nibble = # of bytes to copy (1-11) count of bytes to copy max needed in current format is 3x3 = 9 bytes = (2 tone values, 1 velocity value for each of the 3 voices) * or if the value of the right nibble is higher then 11 or $0B then do the following * $x0 = 00 unused * $xC = 12 signals the repeat count is larger then 16 so use the next byte as the repeat count (left nibble = bytes to copy) * $xD = 13 signals the repeat count is larger then 256 so use the next 2 bytes as the repeat count (left nibble = bytes to copy) * $xE = 14 Header start identifier, which also includes info of the version #, loop counter and if Channel C is a noise/drum track * $xF = 15 signals End of Music data * * Next process the data bytes * * My PSG playback format uses the following format for the data bytes * * ,------------- 0=Note, 1=Volume or channel C Noise/Drum frequency * | ,,----- Channel 00=chan A, 01=chan B, 10=chan C, 11=chan C - Drum/Noise info * | || * |Xxx xx|| x=volume or msb of 12 bit tone info or Xxxxx = 5 bit noise/drum frequency for channel C * 1000 0001 * If it is a Note then it has the 4 msb of the 12 bit tone and the next byte has the 8 lsb's of the 12 bit tone value (so two bytes are always needed for tone data) * Done, the next byte is the next encoded byte... * ************************************** BANK0REG EQU $FF5A * Register for Memory Bank A Range $C000 to $DFFF BANK1REG EQU $FF5B * Register for memory Bank B range $E000 to $FEFF (not used in this program) CONTROL_REG EQU $FF5D * Setup feature of the CoCo PSG * BIT FUNCTION * 7 not used * 6 not used * 5 FLASH programming enable; 0=disabled, 1=enabled * 4 Autostart enable; 0=enabled, 1=disabled * 3 Write Enable (for FLASH/SRAM); 0=disabled, 1=enabled * 2 Gameport B SEL signal (pin 7 of controller port B) * 1 Gameport A SEL signal (pin 7 of controller port A) * 0 YM2149 MASTER CLOCK; 0=2MHz, 1=1MHz YM_RegSel EQU $FF5E * Address for the YM2149 Register Select Port YM_Data EQU $FF5F * Address for the YM Data Port MPI_Reg EQU $FF7F * Address for Multi Pak Interface Slot selector Register opt cd ORG $7B7A * 16k CoCo change ORG Value to $3B7A * 32k CoCo, 64k CoCo or a CoCo 3 change ORG Value to $7B7A LoopSong FCB $FF * How many times do you want to loop the song (1 to 254), $FF=255 = continuous loop LBRA StopPlayback * EXEC jump point to Stop playback from BASIC LBRA Continue * EXEC jump point to Continue playback after stopping playback from BASIC START PSHS D,X,U,CC * Save the registers ORCC #$50 * If you are going to use real IRQ's instead of polling VWAIT then change this section to enable the IRQs * Test if we are running on a CoCo 3, if so we need to go back to RAM mode when exiting our code LDD $FFFE * Get the Reset Interrupt address CMPD #$8C1B * If it's $8C1B then it is a CoCo 3 BNE > LDA #$DF * Since it's a CoCo 3 then we need to self modify the code below, so that we jump back to RAM mode when we exit our code * We use $DF to change the CLR $FFDE (ROM mode) to CLR $FFDF (RAM mode) in the 3 locations STA RomRam1+2 * Initial Setup of IRQ and BASIC hook is setup STA RomRam2+2 * Done playing the notes and setting up the repeat value STA RomRam3+2 * Done playing the song, reset buffer pointer and check repeat value * Setup the CoCoPSG so it doesn't autostart and get the MPI Slot of the CoCoPSG so we can switch back and forth using it and the Disk drive ! LBSR FindCoCoPSG STB CoCoPSGSlot * B now has the slot # (0 to 3) value LDA MPI_Reg * GET Original MPI REG STA MPI * Save the Original MPI value so we can swap back to the Disk controller to continue loading ANDA #%11111100 * SCS TO CoCo PSG SLOT (user selected) - LEAVE *CART/CTS ON ORIGINAL SLOT ORA CoCoPSGSlot * Add the user slot value (0 to 3 at this point) STA MPI_Reg * SWITCH SCS Only LDA #%00010000 * DISABLE AUTOSTART STA CONTROL_REG * WRITE PSG CONTROL REG LDA MPI_Reg * GET MPI REG LSLB * Setup B with the CART/CTS and SCS selection based on the user input # LSLB LSLB LSLB * Shift value (0 to 3) left 4 so that it is for the CART/CTS value ORB CoCoPSGSlot * B now has the proper values for the users CoCo PSG slot for the Cart/CTS and SCS STB CoCoPSGSlot * Save the new value so we can OR the value into it ANDA #%11001100 * CTS and SCS TO SLOT User selected slot ORA CoCoPSGSlot * Add the user slot value (0 to 3 at this point) STA MPIPSG * Save the CoCo PSG MPI selection STA MPI_Reg * Update MPI with new value CLR $FFDE * Go to ROM mode - Must be in ROM mode to read/write the CoCo PSG's 512k RAM * Setup pointer to music data to the start of the song LDA #128 * Set PSG Bank0 to the first 8k Block of it's RAM STA BANK0REG LDX #$C000 STX RAMPointer LDU #Buffer * Set Music data to point to the start of the music data STU PointerM * Save it ! LDD ,X++ * Fill the playback buffer STD ,U++ CMPX #$C000+$110 BNE < RomRam1: CLR $FFDE * Go to ROM mode (self modified to CLR $FFDF) if we are using a CoCo 3 LDA MPI * Change MPI Back to previous (original) slot value STA MPI_Reg * Update MPI with new value ************ * 5 Byte header: * Byte Value * 00-02 'PSG' - Header Identifier * 03 $xx - File version # currently only supprts a value of 01 for version 1.00 * 04 $xx - Number of times to loop this song where xx is: * $00 - Don't change the number of loops value * $01 to $FE - loop this number of times * $FF - loop forever ************ LDU #$400 * Top of screen LDX PointerM * Load X with the current music data pointer in the Buffer space LDD ,X++ * CMPD #$5053 * Start of song data must be "PS" BNE NotPSGFile * Print not a PSG file and Exit if not LDD ,X++ * A='G', B=File version # CMPA #$47 * Start of song file must be "G" BEQ > * If it's equal then it is a PSG file, go check the version # NotPSGFile: BSR PrintERROR * File is not a PSG file, Print ERROR: to the screen BSR PrintString * Go print the text in the next line on screen FCC 'NOT' FCB $60 * Space character code FCC 'A' FCB $60 FCC 'PSG' FCB $60 FCN 'FILE' JMP Exit0 * Exit before we setup IRQ ! CMPB #1 * See if the version # is a 1 BEQ > * This player can only handle version 1 files. If it's a 1 then go play the song :) UnknownVersion: BSR PrintERROR * File is not a version 1 PSG format file, Print ERROR: to the screen BSR PrintString * Go print the text in the next line on screen FCC 'CAN' FCB $60 FCC 'ONLY' FCB $60 FCC 'PLAY' FCB $60 FCC 'VERSION' FCB $60 FCB $71 * '1' - Black foreground and green background to match the CoCo screen #1 FCB $60 FCC 'PSG' FCB $60 FCN 'FILE' JMP Exit0 * File is a PSG file but can't play this version # don't try to play this song, Exit before we setup IRQ PrintERROR: JSR PrintString * Go print the text in the next line on screen FCC 'ERROR' FDB $7A00 * Colon and zero (null) terminater RTS * Return PrintString: LDX ,S * Get address of the Text to print off the stack BRA PS_Skip1 PS_Print1: STA ,U+ PS_Skip1: LDA ,X+ BNE PS_Print1 * Did we find the end terminator (which is zero)? If not go print byte and get another... STX ,S * Put the return address which is just after the text that was printed, back on the stack RTS ! LDA ,X+ * Get the value for Loop counter BEQ > * Skip changing the loop counter if this value is zero STA LoopSong * Otherwise update the LoopSong value ! STX PointerM * Update the file pointer to the start of the music data CLR NoiseFlag * Set the Tone/Noise value for channel C to start setting of 00 = Tone data LDA MPIPSG * Change MPI to CoCo PSG Slot STA MPI_Reg * Update MPI with new value LBSR PlaySetup * Initialize the playback settings CarryOn: * Back to normal MPI Slot LDA MPI * Change MPI Back to previous (original) slot value STA MPI_Reg * Update MPI with new value * If we are going to keep basic running and have this player code running in the background we are going to have to intercept BASIC`s IRQ * and run our code then pass the IRQ control back to BASIC LDX $10D * BASIC jump pointer for IRQ address we will jump back to this address at the end of our play routine STX Back2+1 LDX #IRQEntry * Get our IRQ Start address STX $10D * Store it on the IRQ jump address, so it will now jump to our routine everytime an IRQ is triggered * $FF01 (65281) PIA 0 side A control reg - PIA0AC CoCo 1/2/3 * Bit 7 HSYNC Flag 0=not Sync, 1=Hsync is triggered * Bit 6 Unused * Bit 5 1 * Bit 4 1 * Bit 3 Select Line LSB of MUX * Bit 2 DATA DIRECTION TOGGLE 0 = $FF00 sets data direction 1 = normal * Bit 1 IRQ POLARITY 0 = flag set on falling edge 1=set on rising edge * Bit 0 HSYNC IRQ 0 = disabled 1 = enabled * $FF03 (65283) PIA 0 side B control reg - PIA0BC CoCo 1/2/3 * Bit 7 VSYNC FLAG 0=not Sync, 1=Vsync is triggered * Bit 6 N/A * Bit 5 1 * Bit 4 1 * Bit 3 SELECT LINE MSB of MUX * Bit 2 DATA DIRECTION TOGGLE 0 = $FF02 sets data direction 1=normal * Bit 1 IRQ POLARITY 0=flag set on falling edge 1=set on rising edge * Bit 0 VSYNC IRQ 0=disabled 1=enabled * Setup Cartridge as the sound source * $FF03 bit 3 $FF01 Bit 3 Sound Source * 0 0 DAC * 0 1 Cassette * 1 0 Cartridge *** * 1 1 No Sound * 1 bit audio output is not included here and can be used independantly of the above sources LDA $FF03 * PIA 0 side B control reg - PIA0BC ORA #%00001000 * Bit 3 is the Select Line MSB of MUX set it to 1 for Cartridge source select STA $FF03 * Save settings LDA $FF01 * PIA 0 side A control reg - PIA0AC ANDA #%11110111 * Bit 3 is the Select Line LSB of MUX set it to 0 for Cartridge source select STA $FF01 * Save settings * Also must enable sound output LDA $FF23 * PIA 1 side B control reg - PIA1BC ORA #%00001000 * Set bit 3 to enable sound output STA $FF23 * Save settings Exit0: PULS D,X,U,CC,PC * Now that our Music playing routine is setup we can return to BASIC StopPlayback: PSHS D,CC * Save registers, we are going to return the IRQ back to normal ORCC #$50 * Disable the Interupts * Select the CoCo PSG in the MPI LDB MPIPSG * Change MPI to CoCo PSG Slot STB MPI_Reg * Update MPI with new value * Turn off audio output of the YM2149 LDD #$073F * Channel 7 = Mixer, disable Channel A,B and C, 1 = disabled, keep joysticks enabled STD YM_RegSel * Update the mixer register * Back to normal MPI Slot LDA MPI * Change MPI Back to previous (original) slot value STA MPI_Reg * Update MPI with new value LDD Back2+1 * Get the old IRQ jump pointer STD $10D * Place it back to normal PULS D,CC,PC * Now that our Music playing routine is removed from the IRQ we can return to BASIC Continue: PSHS D,X,U,CC * Save the registers ORCC #$50 * Disable the Interupts * Select the CoCo PSG in the MPI LDB MPIPSG * Change MPI to CoCo PSG Slot STB MPI_Reg * Update MPI with new value LDD #$0738 * Register 7 = mixer Register, #%00111000 * $F8 = Enable Channel A,B and C as Tone data, 0 = selected TST NoiseFlag * Value to keep track if Channel C is currenlty playing Noise or Not, 00 = playing tones, $FF = playing Noise BEQ > * Mixer Channel select * ,,---------I/O * ||,,,------Noise * |||||,,,---Tone * BACBACBA LDB #%00011100 * = $DC Enable Channel C as noise, B and A as Tone data, 0 = selected ! STD YM_RegSel BRA CarryOn * Carry on as if we are starting music playback including setting up the IRQ again, but we don't set the pointer to the music data *************************** * Main loop starts here, checks to see if the Interrupt is a Vsync, if so handle the music playback otherwise jump back to BASIC *************************** IRQEntry: TST $FF03 * Check for 60HZ (Vsync) Interrupt BMI PlayMusic * If IRQ is Vsync (bit 7 of $FF03 is set) then do our play routine Back2: * Continue back to BASIC`s own IRQ JMP >$0000 * This address gets setup from a little self modifying code at the start of the setup code * Force extended mode (using the > sign) just incase the assembler thinks it's in the Direct Page DP area Back: LDA MPI * Change MPI Back to previous (original) slot value STA MPI_Reg * Update MPI with new value PULS D,X,Y,U,CC BRA Back2 PlayMusic: COM Every2nd * We only process sound events every 2nd vsync (save more CPU time) BEQ Back2 * Loop back every 2nd vsync, no need to set the MPI slot, we haven't touched it at this point ;* Show the running time on the screen (This section can be removed, it's only here for testing the player) ; DEC Timer * triggered 30 times every second ; BNE Playnotes * If we haven't reached zero yet then don't update the time ; LDB #30 * reset the timer back to 30 ; STB Timer * save the value ; LDA Seconds2 * check if the ones value of the # of seconds ; CMPA #$39 * if it is a nine then make it a zero ; BEQ > * make it a zero and add to the tens value of the # of seconds ; INCA * Otherwise update ; STA Seconds2 * Save ; BRA Playnotes * Go process music data ;! LDA #$30 * set the ones value to zero ; STA Seconds2 * Save it ; LDA Seconds1 * Get the tens value of the seconds ; CMPA #$35 * check if it is a 5 ; BEQ > * If so then add one to minute value ; INCA * otherwise add 1 to the tens value of the seconds ; STA Seconds1 * save it ; BRA Playnotes * Go process music data ;! LDA #$30 * Set the tens value of the seconds ; STA Seconds1 * to a zero ; LDA Minutes2 * Get the ones value of the minutes ; CMPA #$39 * check if it is a nine ; BEQ > * if so then go add one to the tens of the minute value ; INCA * otherwise increment the ones value of the seconds ; STA Minutes2 * update the value ; BRA Playnotes * Go process music data ;! LDA #$30 * Set the ones value of the minutes ; STA Minutes2 * to zero ; INC Minutes1 * add one the tens value of the minutes ;* End of time on screen display code. The above can be removed * New Encoding: * Encoding byte * left nibble = # of times to repeat 1 to 15 repeat count * * right nibble = # of bytes to copy (1-11) count of bytes to copy * 12 signals the repeat count is larger then 16 so use the next byte as the repeat count (left nibble = bytes to copy) * 13 signals the repeat count is larger then 255 so use the next 2 bytes as the repeat count (left nibble = bytes to copy) * 14 Flip Channel C from/to noise or drum track * 15 signals End of File * Play music Playnotes: DEC RepeatCount+1 * decrement the LSB counter BNE Back2 * if not zero yet then go back TST RepeatCount * Get the value of the MSB number of repeat counter BEQ > * If we are now at zero then go get new notes to play DEC RepeatCount * otherwise decrement the MSB of the counter GoBack: BRA Back2 * Done go back to wait for the vsync trigger (actually every second vsync), no need to set the MPI slot, we haven't touched it at this point * We are now loading another set of commands for the YM chip * Check and Copy data to the buffer so we don't have to keep checking if X>$DFFF to load a new bank of RAM in down below ! PSHS D,X,Y,U,CC * Backup the registers we are going to use LDB MPIPSG * Change MPI to CoCo PSG Slot STB MPI_Reg * Update MPI with new value LDX PointerM * Load X with the current music data pointer in the Buffer space CMPX #Buffer+$100 * See if the pointer is less then $100 LBLO GetNext * skip if less ORCC #$50 * Stop all Interrupts CLR $FFDE * Go to ROM mode LEAX -$100,X STX RestoreX+1 * Store value down below (little self modifying code) LDA RAMPointer * Check if our RAM pointer has reached the end of the PSG 8k block at $E000 INCA CMPA #$DF * BLO > CMPA #$E0 BEQ DoneBlock * We are going to need to load from $DF00 to $DFFF and switch to the next BANK to fill up the extra bit of the Buffer, if we get to this point STA RAMPointer * LDU RAMPointer * Source LDY #Buffer * Destination STS RestoreS1+2 Loop: PULU D,X,S STD ,Y STX 2,Y STS 4,Y PULU D,X,S STD 6,Y STX 8,Y STS 10,Y PULU D,X STD 12,Y STX 14,Y LEAY 16,Y CMPY #Buffer+$100 BNE Loop RestoreS1: LDS #$0000 INC BANK0REG * Point to PSG new memory Bank LDX #$C000 Loop1: LDD ,X++ STD ,Y++ LDD ,X++ STD ,Y++ CMPY #Buffer+$110 BNE Loop1 DEC BANK0REG * Put it back to the last block in PSG memory Bank BRA RestoreX * Change to next Memory Block DoneBlock: INC BANK0REG * Point to PSG new memory Bank LDA #$C0 ! STA RAMPointer * Done2nd: LDU RAMPointer * Source LDY #Buffer * Destination STS RestoreS2+2 ! PULU D,X,S STD ,Y STX 2,Y STS 4,Y PULU D,X,S STD 6,Y STX 8,Y STS 10,Y PULU D,X STD 12,Y STX 14,Y LEAY 16,Y CMPY #Buffer+$110 BNE < RestoreS2: LDS #$0000 RestoreX: LDX #$0000 * Value gets changed by self modifying code above RomRam2: CLR $FFDE * Go to ROM mode (self modified to CLR $FFDF) if we are using a CoCo 3 GetNext: LDB ,X * Get the first byte which has the repeat and data byte count info ANDB #$0F * Clear off the left nibble info CMPB #12 * check if the right nibble is BLO Normal * lower then 12 then the byte is a normal byte where the left nibble is 0 to 15 and the right nibble is the # of music data bytes to copy LBEQ SmallCount * if the right nibble is equal to 12 then handle an 8 bit value for the count CMPB #13 * Check the right nibble is LBEQ BigCount * equal to 13 if so go deal with big count (16 bit) value (next byte holds the repeat count value) CMPB #14 * value of 14 flips Channel C Noise/Tone Flag and sets the mixer type accordingly LBNE Exit1 * Must be 15 so EOF, Reached End of file we are done * If we get here then the value is 14 or $0E COM NoiseFlag * Value to keep track if Channel C is currenlty playing Noise or Not, 00 = playing tones, $FF = playing Noise BEQ NowTone * If it's now zero then it was $FF so switch from Noise to normal Tone mode NowNoise: * Mixer Channel select * ,,---------I/O * ||,,,------Noise * |||||,,,---Tone * BACBACBA LDB #%00011100 * = $DC Enable Channel C as noise, B and A as Tone data, 0 = selected BRA > NowTone: * Mixer Channel select * ,,---------I/O * ||,,,------Noise * |||||,,,---Tone * BACBACBA LDB #%00111000 * = $F8 Enable Channel C as normal Tone data, B and A as Tone data, 0 = selected ! LDA #$07 * A = Channel 7 (Mixer Register), B = Tone/Noise for the Channel C STD YM_RegSel * Update YM Chip with this info LEAX 1,X BRA GetNext Normal: LDA ,X+ * get the # of times to repeat these values, position X to point at the values to be copied LSRA * Shift left nibble to the right nibble LSRA * "" LSRA * "" LSRA * A now has the correct # of times to be repeated STA RepeatCount+1 * Save the repeat count SetByteCount: CLRA TFR D,Y * Y now has the number of bytes to be sent to the YM2149 sound chip CopyBytes: CLRA * Clear A, we will use A to identify the channel LDB ,X+ * Get byte value BMI VolumeChange * If bit 7 is high then this is a volume change RORB ROLA RORB * B now has the most significant value of the tone ROLA * A now has the Channel 0,1,2 LSLA * A = A * 2 which is 0, 2 or 4 (ready for the lsb of the tone) INCA * A is channel 1, 3, or 5 = MSB channel register STD YM_RegSel * Select the A=1,B=3 or C=5 MSB tone register, send msb tone value to the YM2149 sound chip DECA * A is channel 0, 2, or 4 = LSB chennel register LDB ,X+ * Get the LSB tone value STD YM_RegSel * Select the A=0,B=2 or C=4 LSB tone register, send lsb tone value to the YM2149 sound chip LEAY -2,Y * Decrement the counter for bytes sent (we always have two when we change the tone) BNE CopyBytes * has reached 0, if not then go copy more bytes to the YM2149 sound chip DoneAll: STX PointerM * Save the pointer to the music data GoBack1: LBRA Back * Done go back to wait for the vsync trigger (actually every second vsync) VolumeChange: RORB ROLA RORB * B now has the volume info, with bit 5 set (which identified the byte was a volume change) ROLA * A now has the Channel 0,1,2, or 3 CMPA #3 * if A is 3 then it's noise/drums for channel C BEQ MakeNoise * Go play the noise frequency which is in accumulator B bits 4 to 0 ADDA #8 * Make A channel point to A=8,B=9,C=10 ANDB #%00001111 * Strip off the other bits, keep only the 0-15 value STD YM_RegSel * Select the A=8,B=9,C=10 volume register, send volume level value to the YM2149 sound chip LEAY -1,Y * Check if the counter for the number of bytes to send to the sound chip BNE CopyBytes * has reached 0, if not then go copy more bytes to the YM2149 sound chip BRA DoneAll * All done copying data to the YM2149 SmallCount: LDB ,X+ * Get # of bytes to copy from the left nibble LSRB * Shift left nibble to the right nibble LSRB * "" LSRB * "" LSRB * B now has the # of bytes to copy LDA ,X+ * A now has the # of times to repeat the copied values STA RepeatCount+1 * Save the repeat count, position X to point at the values to be copied BRA SetByteCount BigCount: LDB ,X+ * Get # of bytes to copy from the left nibble LSRB * Shift left nibble to the right nibble LSRB * "" LSRB * "" LSRB * B now has the # of bytes to copy LDU ,X++ * Load U with # of repeats count, position X to point at the values to be copied STU RepeatCount * Save the repeat count BRA SetByteCount MakeNoise: LDA #6 * YM register 6 ANDB #%00011111 * strip off bit 5 which signified it was a Volume/Noise value STD YM_RegSel * is noise frequency register, save the frequency * Required each time we make a noise LDD #$0A0B * A = 10 = Channel C, B = 11 = C volume level STD YM_RegSel LEAY -1,Y * Check if the counter for the number of bytes to send to the sound chip BNE CopyBytes * has reached 0, if not then go copy more bytes to the YM2149 sound chip BRA DoneAll * All done copying data to the YM2149 * Setup pointer to music data to the start of the song Exit1: CLR $FFDE * Go to ROM mode LDA #128 * Set PSG Bank0 to the first 8k Block of it's RAM STA BANK0REG LDX #$C000 * Skip the 5 byte header info STX RAMPointer LDU #Buffer+5 * Set Music data to point to the start of the music data, skip 5 byte header STU PointerM * Save it LDU #Buffer ! LDD ,X++ STD ,U++ CMPX #$C000+$110 BNE < RomRam3: CLR $FFDE * Go to ROM mode (self modified to CLR $FFDF) if we are using a CoCo 3 CLR NoiseFlag * Set Channel C tone/noise flag to tone LDA LoopSong CMPA #$FF * $FF = loop forever BEQ > DEC LoopSong BNE > * If we reached 0 in our loop counter then stop playback BSR PlaySetup LDX Back2+1 * Get the old IRQ jump pointer STX $10D * Place it back to normal GoBack2: LBRA Back * Done go back to wait for the vsync trigger (actually every second vsync) ! BSR PlaySetup * Reset everything to start the song again BRA GoBack2 PlaySetup: * Clear channel repeat note counters LDD #$0001 * Clear counter STD RepeatCount * Clear the counter for how many times the current notes will play until they need to be changed ************** * Set defaults for the YM2149 * ,,---------I/O * ||,,,------Noise * |||||,,,---Tone * BACBACBA LDD #$0738 * Register 7 = mixer Register, #%00111000 * $F8 = Enable Channel A,B and C as Tone data, 0 = selected STD YM_RegSel ZeroVolume: LDD #$0800 * Register 8 = Volume Register for Channel A, Volume Level 0=off to 15=full, logarithmic curve STD YM_RegSel INCA * Register 9 = Volume Register for Channel B STD YM_RegSel INCA * Register 10 = Volume Register for Channel C STD YM_RegSel ;* This is more Timer display related code that can be removed along with the other Timer related section of code, above ; LDD #$3030 * ascii '00' ; STD Minutes1 * Start showing 00 minutes ; STD Seconds1 * Start showing 00 seconds ; CLR Every2nd * Process sound every 2nd Vsync IRQ hit ; LDB #30 * Vsync is triggered 60 times a second, since we only process every second vsync we count down 1/30th of a second ; STB Timer * store it ; LDB #': * Draw the colon on screen between the minutes and the seconds ; STB Minutes2+1 * store it ;* End of Time display related code that can be removed if you don't want to see a timer on the screen. RTS ************************************************************************************************************** * Detect what slot the CoCoPSG is in the Multi-Pak Interface * Using Ed Snider's idea to detect which slot the CoCoPSG is plugged into in the Multi-Pak Interface * * All registers are preserved except B * Result is in the B accumulator * If B=$FF then no CoCoPSG is in any slot of the MPI * otherwise B = the slot where the CoCoPSG is in -1 (0 to 3) where 0 = Slot 1,1 = Slot 2,2 = Slot 3,3 = Slot 4 ************************************************************************************************************** FindCoCoPSG: PSHS A,X,CC ORCC #$50 LDA $FF7F * Get the original MPI_Register value (MPI Register) PSHS A * Save it for restore later LDB #%11111100 * We will AND this value to select through the different MPI slots SCS selector CheckSlot: STB $FF7F * Select Slot (MPI Register) PSHS B * Save B LDD #$06FF * Store $FF in registers 6 to 0 of the YM2149 CS1: STD $FF5E * To see if the sum is 841 since Registers 0,2,4 store 8 bit values, 1,3,5 store 4 bit values (YM_Register Select)(YM_DATA) DECA * and register 6 stores a 5 bit value BPL CS1 * Keep adding 255 to each byte LDA #06 LDX #$0000 CS2: STA $FF5E * Select the different registers (6 ot 0) (YM_Register Select) LDB $FF5F * Get the stored value of this register (YM_DATA) ABX * Add B to X to keep a running total DECA * Total stored on the CoCoPSG will be 255+15+255+15+255+15+31 = 841 BPL CS2 * Count down A from 6 to 0 PULS B * Restore B CMPX #841 * If the sum is 841 then this is the CoCo PSG slot BEQ FoundCoCoPSG * If X=841 then we found the slot with CoCo PSG :) CMPB #$FF * Check if we just checked slot 4 BEQ ExitPSGCheck * If so then no CoCo PSG is detected exit with B=$FF :( INCB * Else, load next slot value BRA CheckSlot * Go check next slot FoundCoCoPSG: ANDB #%00000011 * B now has the slot # (0 to 3) value ExitPSGCheck: PULS A * Get the original MPI_Register value STA $FF7F * Restore the original value (MPI Register) PULS A,X,CC,PC * B = slot # -1 or $FF if not found ************************************************************************************************************** EndPlayerCode: * Variable storage RepeatCount FDB $0001 * Pointer to RAM location for keeping track of music playback Every2nd FCB $00 * byte to keep track of every 2nd vsync PointerM FDB Buffer * Pointer to Music Data PSGRAMPtr FCB 128 * PSG RAM block pointer 128 = first block of 8k bytes RAMPointer FDB $C000 * Pointer to CoCo PSG RAM Bank A Buffer RMB $110 * Temporary Buffer needed since we are using the PSG and reading bytes might go beyond $DFFF NoiseFlag FCB $00 * Value to keep track if Channel C is currenlty playing Noise or Not MPI FCB $00 * Original MPI Program Register value MPIPSG FCB $00 * CoCo PSG MPI Program Register value CoCoPSGSlot RMB 1 * Memory location where BASIC will store the SLOT location of the CoCoPSG in the MPI ;* Timer related pointers, Can be removed as you probably don't require a timer to be shown on screen in your game ;Timer FCB 30 * used for the Clock counter counts down from 30 every time play loop is entered. When it hit's zero a second has passed ;Minutes1 EQU $420-5 * Location to display timer on screen (minutes and seconds) ;Minutes2 EQU Minutes1+1 ;Seconds1 EQU Minutes1+3 ;Seconds2 EQU Minutes1+4 END START ************************************** * Info about the YM2149 used inside Ed Snider's CoCo PSD Cartridge for the Tandy Color Computer * The YM2149 sound chip is a clone of the AY-3-8910 Sound chip with a few differences * * The YM2149 has three sound channels, A, B & C any of these three channels can output either Tone or Noise which is selectable by the user * * Specs for the YM2149 is here: * http://www.ym2149.com/ym2149.pdf * * Info on playing back ym format songs is here: * http://leonard.oxg.free.fr/ymformat.html * ************************************** * The YM2419 is used inside Ed Snider's CoCo PSG Cartridge for the Tandy Color Computer * * Registers * --------- * * The AY-3-8910/8912 contains 16 internal registers as follows: * * Register Function Range * 0 Channel A fine pitch 8-bit (0-255) * 1 Channel A course pitch 4-bit (0-15) * 2 Channel B fine pitch 8-bit (0-255) * 3 Channel B course pitch 4-bit (0-15) * 4 Channel C fine pitch 8-bit (0-255) * 5 Channel C course pitch 4-bit (0-15) * * 6 Noise pitch 5-bit (0-31) * 7 Mixer 8-bit (see below) * * 8 Channel A volume Bits 0 to 3 = 4-bit (0-15, see below) if bit 4 is set it signals this channel is using the Envelope info for the volume * 9 Channel B volume Bits 0 to 3 = 4-bit (0-15, see below) if bit 4 is set it signals this channel is using the Envelope info for the volume * 10 Channel C volume Bits 0 to 3 = 4-bit (0-15, see below) if bit 4 is set it signals this channel is using the Envelope info for the volume * * 11 Envelope fine duration 8-bit (0-255) * 12 Envelope course duration 8-bit (0-255) * 13 Envelope shape 4-bit (0-15) * * 14 I/O port A 8-bit (0-255) * 15 I/O port B 8-bit (0-255) * * Note Frequency calculation * * The output frequency is equal to the IC's incoming clock frequency divided by 16 and then further divided by the number written to the course and fine pitch registers. * The higher the number written to these, the lower the pitch. * * For example 1Khz is required and the CoCo PSG is using 2Mhz timing (Default) switchable to 1Mhz * 2Mhz = 2000000 / 16 * Tone (Hz) * * Example if you want a tone of 440 Hz then take 440 * 16 = 7040 * Next do 2000000/7040 = 284.09 * Make the result an integer 284.09 is closer to 284 then 285 so use 284. Transpose the value 284 into a 12 bit number so it would be: * * Course values Fine Value * Decimal 1x256 + 28 * Hexidecimal $01 + $1C * Binary 0001 + 00011100 * * Now that we know our Course (Most Significant) and the Fine (Least Significant) value we select which Channel we want to play back the 440 Hz tone * we could use A, B or C. If you select channel B then we will need to send the numbers to Registers 2 & 3 as per the chart above. * You could change the values of the course value and then the fine value, but I think it's best to change the fine value first, since the change isn't as drastic as changing the * course value, even though it's done in the microseconds the change might be audible. * * This code sets the tone Frequency for audio channel B: * LDA #2 * STA $FF5E * Select register 2 = B Fine value * LDA #28 * STA $FF5F * Store value 28 into B Fine register * LDA #3 * STA $FF5E * Select register 3 = B Course value * LDA #1 * STA $FF5F * Store value 1 into the B Course register * * We should also set the volume level desired for the B Channel by doing the following: * LDA #9 * STA $FF5E * Select register 9 = B Volume register * LDA #15 * STA $FF5F * Store value 15 into B volume register, 15 is the loudest level setting, 0=lowest volume level * * Lastly we enable or disable the type of output we want from the B Channel using register 7 using the info from the chart below * - The mixer (register 7) is made up of the following bits (low=enabled) the AY-3-8912 ignores bit 7 of this register. * _ _ * I/O I/O Noise Noise Noise Tone Tone Tone * B A C B A C B A * Bit: 7 6 5 4 3 2 1 0 * * To enable Channel B as Tone output we do the following: * LDA #7 * STA $FF5E * Select register 7 = Mixer register * LDA #$FD * $FD = 11111101 - Setting a value low (0) enables that option. We could enable C,B & A with a value of 11111000 or $F8 * STA $FF5F * Store value $FD to register 7 * * At this point the tone will play continuously until you change the value of the tone or set the volume to 0 or change the Mixer register to turn off Channel B output * * Notes: * - The AY-3-8912 does not contain register 15. * - The volume registers (8, 9 and 10) contain a 4-bit setting but if bit 4 is set then that channel uses the envelope defined by register 13 and ignores its volume setting. * * Envelopes * --------- * The AY-3-8910/8912 contains the following preset envelopes or waveforms (set using control register 13). Note that these affect volume only and not the pitch: * * 0 \__________ single decay then off * * 4 /|_________ single attack then off * * 8 \|\|\|\|\|\ repeated decay * * 9 \__________ single decay then off * * 10 \/\/\/\/\/\ repeated decay-attack * _________ * 11 \| single decay then hold * * 12 /|/|/|/|/|/ repeated attack * __________ * 13 / single attack then hold * * 14 /\/\/\/\/\/ repeated attack-decay * * 15 /|_________ single attack then off * ***************************************************