BANK0REG EQU $FF5A * Register for Memory Bank A Range $C000 to $DFFF BANK1REG EQU $FF5B * Register for memory Bank B range $E000 to $FEFF CONTROL_REG EQU $FF5D * Setup feature of the CoCo PSG * BIT FUNCTION * 0 YM2149 MASTER CLOCK; 0=2MHz, 1=1MHz * 1 Gameport A SEL signal (pin 7 of controller port A) * 2 Gameport B SEL signal (pin 7 of controller port B) * 3 Write Enable (for FLASH/SRAM); 0=disabled, 1=enabled * 4 Autostart enable; 0=enabled, 1=disabled * 5 FLASH programming enable; 0=disabled, 1=enabled * 6 not used * 7 not used YM_SEL EQU $FF5E YM_DATA EQU $FF5F MPI_Reg EQU $FF7F * Address for Multi Pak Interface Slot selector Register FixClose EQU $0E00 * Bytes BASIC copied the original CLOSE routine address to UserCoCoPSGSlot EQU $E02 * BASIC program will as the user what slot the CoCo PSG is in and store the value here. This value * will be in the range 0 to 3 * Store the length of the PSG Song Data Could be upto 512k (actually what will fit on a disk 150kish) * 24 bit value: * 3 byte value first byte is Int(Value/65536) * second byte Int((Value/65536 - Int(Value/65536)) / 256) * third byte is (((Value/65536 - Int(Value/65536)) / 256) - Int((Value/65536 - Int(Value/65536)) / 256) * 256) ORG $0E03 LOF FCB $00 * Size of PSG Song data MSB FDB $0A77 * Second most sigificant Byte and the LSB MPI FCB $00 * Original MPI Program Register value MPIPSG FCB $00 * CoCo PSG MPI Program Register value ************************************************************************************************************** * Detect what slot the CoCoPSG is in the Multi-Pak Interface * Using Ed Snider's idea to detect which slot the CoCoPSG is plugged into in the Multi-Pak Interface * * All registers are preserved except B * Result is in the B accumulator * If B=$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 not 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 $FF if not found ************************************************************************************************************** START PSHS D,X,U * Save our registers BSR FindCoCoPSG * Go find the slot the CoCo PSG is plugged into in the MPI CMPB #$FF * If B=$FF then no CoCoPSG was detected BNE > NoCOCOPSG: LDU #$400 BSR PrintString * Go print the text in the next line on screen FCC 'ERROR' FCB $7A FCC 'NO' FCB $60 * Space character code FCC 'COCOPSG' FCB $60 FCN 'FOUND' PULS D,X,U * Should let BASIC know that no CoCo PSG was detected RTS 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 ! LDX $FFFE * Check if we are running on a CoCo 3 CMPX #$8C1B BEQ > LDA #$DE * Change location in the program (self modify code) so they don't go into RAM mode STA ROMRAM+2 * CoCo 1 or 2 should stay in ROM mode STA ROMRAM1+2 * CoCo 1 or 2 should stay in ROM mode ! STB UserCoCoPSGSlot * Save the slot # (0 to 3) where the CoCo PSG is 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 UserCoCoPSGSlot * Add the user slot value (0 to 3 at this point) STA MPI_Reg * SWITCH SCS Only LDA $FF5D * GET PSG CONTROL REG ORA #%00010000 * DISABLE AUTOSTART STA $FF5D * 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 UserCoCoPSGSlot * B now has the proper values for the users CoCo PSG slot for the Cart/CTS and SCS STB UserCoCoPSGSlot * Save the new value so we can OR the value into it ANDA #%11001100 * CTS and SCS TO SLOT User selected slot ORA UserCoCoPSGSlot * 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 LDA #128 * Set PSG RAM pointer to 0 STA BANK0REG LDB LOF * B is the MSB of the PSG music data size INCB * Add one so the check EOF loop below is a little more efficient STB LOF LDX LOF+1 * X is the second most significant and the LSB of the PSG music data size ROMRAM: CLR $FFDF * Go to RAM mode If CoCo 3 is detected, otherwise this will be changed to $FFDE (self mod code above) Loop0: LDU #$C000 * Start of PSG Bank 0 RAM Loop1: LDA #%00010000 * Disable writing to the PSG 512k RAM STA CONTROL_REG * Update PSG Disable writing to the PSG 512k RAM LDA MPI * Change MPI to Disk Controller Slot STA MPI_Reg * Update MPI with new value JSR $A176 * Read a byte from the file into A (CONSOLE IN) ORCC #$50 * Disable the interrupts CLR $FFDE * Go to ROM mode LDB MPIPSG * Change MPI to CoCo PSG Slot STB MPI_Reg * Update MPI with new value LDB #%00011000 * Enable writing to the PSG 512k RAM STB CONTROL_REG * Update PSG Enable writing to the PSG 512k RAM STA ,U+ ROMRAM1: CLR $FFDF * Go to RAM mode If CoCo 3 is detected, otherwise this will be changed to $FFDE (self mod code above) ANDCC #%1010111 * Enable the interrupts LEAX -1,X * Decrement the PSG Music data size counter BNE > * If not zero jump to check if we have reached the end of the PSG Bank A DEC LOF BEQ CleanUp * IF PSG Music data has all been loaded then jump to clean up routine ! CMPU #$E000 BLO Loop1 INC BANK0REG * set to the next PSG Bank A block of RAM BRA Loop0 CleanUp: LDA #%00010000 * Disable writing to the PSG 512k RAM STA CONTROL_REG * Update PSG LDA MPI * Change MPI to Disk Controller Slot STA MPI_Reg * Update MPI with new value LDD FixClose * restore close file pointer address STD $0177 PULS D,X,U * Restore our registers JMP $0176 * Jump back to the Close file routine that we intercepted ORG $0177 FDB START * Change the Close File jump address to point to this program END START