Connecting a PC-card to a C64. In 1988 I realised an interface for the C64 which enabled me to use PC-card. The first use I had in mind was connecting a MFM-harddiskcard to the C64. The project failed due to the fact that I had to write my own program for the controller. In those days every controller had its own program fitted in an EPROM. After some weeks my controller died (in the PC of my company) and all work was for nothing as I could not use it for the next controller. Having the interface, I started to use it in combination with a MGP- and a Multi-I/O-card. The first one enabled me to use a 80 columns screen and printerport. The second one to use fast speed RS232 and the floppydrive. I did some trials with the drive but when I started to use PC-Disk 1.0, I prefered to spend my time on other projects. First have a look at the pinouts of the 8-bits ISA BUS: Pin Signal Description Direction -------------------------------------------------------------------------- A1 -I0CHCK I/0 channel check In A2 SD7 Data bit 7 In/Out A3 SD6 Data bit 6 In/Out A4 SD5 Data bit 5 In/Out A5 SD4 Data bit 4 In/Out A6 SD3 Data bit 3 In/Out A7 SD2 Data bit 2 In/Out A8 SD1 Data bit 1 In/Out A9 SDO Data bit 0 In/Out A10 -I0CHRDY I/0 Channel ready In Al1 AEN Address enable Out A12 SA19 Address bft 19 Out A13 SA18 Address bit 18 Out A14 SA17 Address bit 17 Out A15 SA16 Address bit 16 Out A16 SA15 Address bit 15 Out A17 SA14 Address bit 14 Out A18 SA13 Address bit 13 Out A19 SA12 Address bit 12 Out A20 SA11 Address bit 11 Out A21 SA1O Address bit 10 Out A22 SA9 Address bit 9 Out A23 SAS Address bit 8 Out A24 SA7 Address bit 7 Out A25 SA6 Address bit 6 Out A26 SAS Address bit 5 Out A27 SA4 Address bit 4 Out A28 SA3 Address bit 3 Out A29 SA2 Address bit 2 Out A30 SA1 Address bit 1 Out A31 SA0 Address bit 0 Out B1 GROUND B2 RESET DRV Active high reset Out B3 +5Vdc B4 IRQ2 Interrupt request 2 In B5 -5Vdc B6 DRQ2 DMA request 2 In B7 -12Vdc B8 -CARD SLCTD Card selected In B9 +12Vdc B10 GROUND B11 -MEMW Memory write Out B12 -MEMR Memory read Out B13 -IOW I/O write Out B14 -IOR I/O read Out B15 -DACK3 DMA acknowledge 3 Out B16 DRQ3 DMA request 3 In B17 -DACK1 DMA acknowledge 1 Out B18 DRQ1 DMA request 1 In B19 -REFRESH Refresh Out B20 CLOCK System clock Out B21 IRQ7 Interrupt request 7 In B22 IRQ6 Interrupt request 6 In B23 IRQ5 Interrupt request 5 In B24 IRQ4 Intertupt request 4 In B25 IRQ3 Interrupt request 3 In B26 -DACK2 DMA acknowledge 2 Out B27 T/C Terminal count Out B28 ALE Address latch enable Out B29 +5Vdc B30 OSC Clock 14.31818Mhz Out B31 GROUND IOCHCK is an active (L) signal meant to signal the PC that there is a memory parity error. On the end this signal triggers the NMI-input of the CPU. As so we can use the NMI-input of the expansionport. SD0..7 is connected to D0..7. IOCHRDY signals the CPU that the card needs more time for whatever it is doing. This is realised by holding the CPU. The 6510 has such a feature as well but the problem is that the corresponding input can be found at the expansionport. To be honest, I never saw a card having this line. I did not use this line. AEN tells a card that an (H) and the use of the I/O lines means there is a DMA transfer in progress. As the C64 has no DMA capabilities onboard, we can tie this line to GND. But I thinking of the idea of adding a 8237 DMA-controller to a C=. So in the future.... A PC-card uses 20 addresslines but the C64 only has 16. And to make it worse, we only have a range of 512 free to use for our own purposes. In 1988 I hacked my C64 by de-mirroring the VIC and SID, freeing 1.5 KB. I used 512 bytes for my interface. Why only 512? To remain compatible with users who didn't want to hack their C64. The idea was to use 256 bytes for the swap area and to reserve a part of the other 256 bytes for I/O. The above meant that I needed to provide another 12 addresslines using buffers. In 1988 I used two 74LS374s. No read back possebility (less soldering, used RAM). RESET DRV is an active (H) reset signal. Generated by using the resetline of the C64 thru a 7406. IRQ2..7 are active (H) interrupt inputs. I ORred these signals and connected them to the IRQ-input thru a 7406. I also connected them to a 74LS541 to determine which IRQx was activated. MEMR, MEMW, IOR, IOW. The INTEL and ZILOG CPUs sepperated I/O and memory handling. But they also used these lines to inform connected IC's when data was valid or not. The 65xx uses CLK2 for this purpose. I made the difference between I/O and memory by using bit 7 of the 374 used to generate A16..19. I used a 74LS138 to generate the needed signals: A - CLK2 B - bit 7 C - R/W /G1 - IO2 /G2 - IO2 G - BA Y0..3 -> no meaning Y4 -> MEMW Y5 -> MEMR Y6 -> IOW Y7 -> IOR DRQx, DACKx, REFRESH, T/C and ALE not used in the 8 bits version. CLOCK: I connected CLK2 to it. Some remarks are at the end. In 1989 I made a 64 KB SRAM card to use in an AT. This enabled me to use more memory in a simple way. I also got interested in using memory expansion cards for the C64. So I started to make a 16 version. 16-bit AT extension ------------------- C1 SBHE System bus high enable In/Out C2 LA23 Address bit 23 (unlatched) In/Out C3 LA22 Address bit 22 (unlatched) In/out C4 LA21 Address bit 21 (unlatched) In/Out C5 LA20 Address bit 20 (unlatched) In/Out C6 LA19 Address bit 19 (unlatched) In/Out C7 LA18 Address bit 18 (unlatched) In/Out C8 LA17 Address bit 17 (unlatched) In/Out C9 -MEMR Memory read In/Out C10 -MEMW Memory write In/Out C11 SD08 Data bit 8 In/Out C12 SD09 Data bit 9 In/Out C13 SD10 Data bit 10 In/Out C14 SD11 Data bit 11 In/Out C15 SD12 Data bit 12 In/Out C16 SD13 Data bit 13 In/Out C17 SD14 Data bit 14 In/Out C18 SD15 Data bit 15 In/Out D1 -MEM CS16 Memory 16-bit chip select In D2 -I/O CSI6 I/O 16-bit chip select In D3 IRQ10 Interrupt request 10 In D4 IRQ11 Interrupt request 11 In D5 IRQ12 Interrupt request 12 In D6 IRQ15 Interrupt request 13 In D7 IRQ14 Interrupt request 14 In D8 -DACK0 DMA acknowledge 0 Out D9 DRQO DMA request 0 In D10 -DACK5 DMA acknowledge 5 Out D11 DRQ5 DMA request 5 In D12 -DACK6 DMA acknowledge 6 Out D13 DRQ6 DMA request 6 In D14 -DACK7 DMA scknowledge 7 Out D15 DRQ7 DMA request 7 In D16 +5Vdc D17 -MASTER Used with DRQ to gain control of system In D18 Ground SHBE signals the card wether an 8 or 16 bits transfer is in progress. Used bit 6 of the above 374. The AT-extension provides 4 extra addresslines. 16 MB was such a enormous amount of memory those days, that I only provided A20..21 using the left over bits of the 374 mentioned above. Otherwise I had to add an extra 374 just for the IO/MEM differentiation and SHBE. The expansion as MEMx signals as well. In AT the original MEMx signals are only active when addressing the range up to $10000. I used some OR-gates and an invertor to determine if the address was in this range and mixed this signal with the MEMx signals for the 8-bit part using OR-gates. IRQ10..14: added an 541 plus logic to activate IRQ DRQx, DACKx, MASTER: not used. D8..15: The trick I used here I later used with my IDE-interface. I added added two 74ALS573s. One was used to store the data form the C64 towards D8..15. The data was outputted during _every_ write action. The other 573 was used for the opposite direction. Here the data was only stored during a read action of the PC-card. I/O CS16, MEM CS16: not used as the only had an function for the internal of a PC. Reading/writing a WORD from/to an 8-bits card implies that the _HARDWARE_ (and _not_ the CPU) performs two 8 bit reads/writes from/to the card. These lines signaled the hardware that the card was able to deliver 16 bits at once and no tricks were needed. Remark: writing a BYTE to an odd address of an 8-bits card resulted writing the byte to D0..D7. With a 16-bits card this resulted in writing to D8..15. I thought about implementing this as a HW-feature, but as I had to write the software for any card all myself any way, I prefered the SW-solution. My risk: if I changed a 8-bit card for an 16-bit version, I had to rewrite the SW for this card. The only cards I had in mind anyway were a memory-expansion-card and AT-harddiskcard. I have little experience with this card as in 1991 I was scheduled to go to Kouwait. So I packed my things to be stored for the time being there. Only to see a big hole in wall of our office on television the day before my flight, Saddam probably didn't like the furniture :( Anyway, only after finding a new appartment, I found out a box was missing. Two of the things in that box were the above cards :(((( Remarks regarding the hardware: As mentioned I used 574s for the cards. Nowadays I would use 6526 as I have enough of them. Soldering two 574s means soldering 40 pins. Soldering a 6526 (or 6821) means 40 pins as well but the advantage is readback facility and some extra lines. Groetjes, Ruud http://home.hccnet.nl/g.baltissen/index.htm - This message was sent through the cbm-hackers mailing list. To unsubscribe: echo unsubscribe | mail firstname.lastname@example.org.
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