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Text File | 1990-02-12 | 15.0 KB | 462 lines

HARD DISK DRIVE ON A C-64 PREFACE This is an explanation of one method of connecting a hard disk drive to the Commodore 64 computer using a Western Digital controller card. Obviously there are many ways in which to approach this task and each will have its merits. Since there may be a lack of compatibility with some existing software this project may be of limited value and each one should give careful consideration to the the pros and cons before investing in the project. With this disclaimer in mind, ever onward. The task of connecting a Western Digital hard disk controller to the C64 is rather simple but does require basic soldering and wiring skills. Remember that it is possible to damage the C64 and/or the controller card with improper wiring. The cost of this project is very possibly more than trivial so proceed with caution. One last time, is it worth the risk and effort? The availability of a good reference manual with the pin out of the expansion port as well as a reference for the PC bus will help to understand the following directions. Before starting with the details an overview of the controller card might be in order. A Western Digital WX1 controller was used in the prototype but the WX2 should work as well. Don't be concerned as to what BIOS ROM is on the card since it will not be used. There are several different versions of the controller cards but all should work. The controller writes 17 sectors each of 512 bytes on each track which contrasts with the 128 byte sectors on the 1541. Dependent upon the version of the controller card the drives supported can have up to 8 or 16 heads and a maximum of 1024 cylinders. The software support described later assumes a limit of 8 heads. A limit of 8 heads will allow for the attachment of a drive with a capacity of greater than 30 megabytes. Additionaly 2 drives can be attached to a controller and more than one controller could be installed offering a great amount of storage relative to a 1541 diskette. A 10 megabyte drive could possibly be a good choice since often a used one can be bought at a very reasonable price. The controller supports 19 commands for reading, writing, formating, diagnostics, and etc. With the exception of the WX1GEN card there is an eight position header which is normally used to select which drive parameters to use out of a table. The 'hard disk kernal' doesn't use these. It reads the configuration off sector zero. The FORMAT program is responsible for writing the information on the first sector. HARD DISK DRIVE ON A C-64 2 Okay, now what is needed before starting the adventure? The list follows. A Western Digital WX1 or WX2 controller card. A hard disk drive compatible with the controller card. An enclosure with power supply for the hard disk drive. Cables to connect the controller to the drive. (1 34 conductor and 1 20 conductor) An edge card with .1" contact centers to plug into the expansion port. Radio Shack has one new in 1989 (276-192) which will work. One 31/62 pin pc mount edge connector with .1" centers for the controller card. (A right angle would be nice.) One 14 pin IC socket. One 74LS04 IC. One .01 uf 10 volt bypass capacitor. Some 30 gauge or so wire wrap or similar wire. Possibly a separate power supply for the controller card. It requires +5 and +12 volts. This can be obtained from the supply used for the drive. Radio Shack has a supply with +5vdc, -5vdc, and +12vdc which was originally used on a Coleco which works rather well. HARD DISK DRIVE ON A C-64 3 The pertinent pin out for the controller card follows: A2 D7 (data bit seven) A3 D6 (data bit six) A4 D5 (data bit five) A5 D4 (data bit four) A6 D3 (data bit three) A7 D2 (data bit two) A8 D1 (data bit one) A9 D0 (data bit zero) A22 A9 (address line nine) A23 A8 (address line eight) A24 A7 (address line seven) A25 A6 (address line six) A26 A5 (address line five) A27 A4 (address line four) A28 A3 (address line three) A29 A2 (address line two) A30 A1 (address line one) A31 A0 (address line zero) B1 GROUND B2 RESET (active high) B3 +5VDC B9 +12VDC B10 GROUND B13 -IOW (I/O WRITE active low) B14 -IOR (I/O READ active low) B29 +5VDC B31 GROUND To locate the pins on the controller card place it component side up with the fingers facing you. Pin A1 will be on the far right and A31 will be on the far left. B1, B2, etc. are directly behind the A pins on the opposite side of the card. Most if not all the cards will have A1 marked as such. The C64 bus needs to be mapped to the contoller which requires some of the signals to be inverted. The 74LS04 IC is used to invert the required signals and to derive the IOR and IOW from the C64 R/W line. HARD DISK DRIVE ON A C-64 4 The pins of interest on the expansion port are: 1 GROUND 2 +5 volts dc 3 +5 volts dc 5 R/-W (READ if high, WRITE if low) 7 -I/O1 (I/O BLOCK 1, active low) or 10 -I/O2 (I/O BLOCK 2, active low) Either pin 7 or 10 is used for selecting the I/O address of the controller. 14 D7 (DATA BIT 7) 15 D6 (DATA BIT 6) 16 D5 (DATA BIT 5) 17 D4 (DATA BIT 4) 18 D3 (DATA BIT 3) 19 D2 (DATA BIT 2) 20 D1 (DATA BIT 1) 21 D0 (DATA BIT 0) 22 GROUND A GROUND R A7 (ADDRESS line 7) S A6 (ADDRESS line 6) T A5 (ADDRESS line 5) U A4 (ADDRESS line 4) V A3 (ADDRESS line 3) W A2 (ADDRESS line 2) X A1 (ADDRESS line 1) Y A0 (ADDRESS line 0) Z GROUND Looking at the back of the C64 at the expansion slot, pin 1 is on the right top, pin 22 is on the top left, pin A is on the bottom right, and pin Z is on the bottom left. NOTE that all the alphabet isn't used in numbering the bottom pins, refer to a C64 description for the proper pins. HARD DISK DRIVE ON A C-64 5 Armed with the above information it's time to start putting the adapter together. First trim the fingers of the edge card down to where it will properly fit into the expansion port 22/44 pin socket. CAUTION! Make sure it fits properly. A short can blow the fuse in the power supply. The RS-276-192 card mentioned earlier is made to fit a 36/72 pin socket. Next mount the 14 pin IC socket close to the fingers on the card followed by the 31/62 pin controller socket. As mentioned in the parts list a right angle would be great since it would allow the controller card to be mounted horizontally, but may be difficult to find. A wire wrap socket could be used and the pins bent to right angles and trimmed properly. Connect the fingers to the sockets as indicated below. C64 CONTROLLER 1 B31 GROUND 14 A2 D7 15 A3 D6 16 A4 D5 17 A5 D4 18 A6 D3 19 A7 D2 20 A8 D1 21 A9 D0 22 B1 GROUND A B10 GROUND R A24 A7 S A25 A6 T A26 A5 U A27 A4 V A28 A3 W A29 A2 X A30 A1 Y A31 A0 Z B10 GROUND Make the following connections to the 14 pin IC socket. IC C64 CONTROLLER 1 C -RESET 2 B2 RESET 3 7 or 10 (see text) IO1 or IO2 4 A22 & A23 address bits 8 and 9 5 5 READ/-WRITE 6 B14 -IOR 7 1 GROUND 8 B13 -IOW 9 connect to IC pin 6 10,11,12,13 no connection 14 2 & 3 +5VDC HARD DISK DRIVE ON A C-64 6 The next step is to connect the +5VDC and +12VDC to the socket for the controller card. This power can be taken from the power supply in the hard disk enclosure or from a separate supply. Radio Shack has an inexpensive power supply that was made for Coleco which has +5VDC, +12VDC, and -5VDC. Wherever it comes from, wire the +5VDC to controller pins B3 and B29, the +12VDC to controller pin B9, and GROUND to controller pins B1, B31, and B10. With the wiring of the adapter complete it is time to connect a hard disk to the controller. Connect the 34 conducter cable to the header labeled J1 on the controller and the first drive to the 20 pin header J2. The second drive connects to header J3 and to a second edge connector on the 34 conducter cable. These cables must be plugged in so that PIN 1 from the controller is connected to PIN 1 of the drive, etc. Most cables have a solid colored side coresponding to the PIN 1 side and some may be keyed such as to only fit the proper way. The cables can have a maximum length of around 10 feet. The drive connected to J3 will need its address switches or jumpers to be set for drive 2 while the drive in J2 will need to have its switches set for drive 1. Plug the controller card into the adapter and the adapter into the C64 expansion port. Apply power to the drive and controller card along with power to the 64. If all is well so far then the C64 should come up and run. If not, something is probably either mis-wired or shorted. Double check all the connections. Remember that a short could blow a fuse either in the C64 or in the power supply block. Since most of the Commodore supplies are not repairable, a blown fuse in the power supply is bad news to say the least. Once the hardware is up and apparently working it is time to start with the software. Available with this package is the 'hard disk kernal'. This kernal has the support for the nineteen commands. For a better explanation refer to the source for the kernal and read the comments. There is a control block used to communicate with the controller called the Drive Control Block (DCB) which is 6 bytes long. The format of the DCB is: Byte 0 - command code. Byte 1 - drive number (0 or 1) and head number. Byte 2 - Most significant 2 bits of the cylinder address and the sector number. Byte 3 - Least significant 8 bits of the cylinder address. Byte 4 - Number of sectors to read or write, or the interleave if formating. Byte 5 - Step rate for moving the heads (seeking). The DCB will need to be updated before reading or writing. The 'hard disk kernal' passes this information on to the controller. Some additional information is appended to the DCB which is used by the 'hard disk kernal' which is HARD DISK DRIVE ON A C-64 7 documented in the comments of the source for the kernal. The success of a call to the hard disk kernal is indicated by CARRY being clear upon return, and CARRY set for failure. Reference the source for the programs for examples of some of the calls.