MSD-SD2 schematic, service information and operators manual on 7-6-05.
MSD-SD2 schematic, service information and operators manual on 7-6-05 Look for the MSD-SD2 schematic, service information and operators manual on my schematics website: http://staff.washington.edu/rrcc 7-6-05 Quoting from the operators manual, except for my additions for clarity: CHANGING THE DISK DRIVE DEVICE NUMBER The device number on the MSD SUPER DISK DRIVE (dual: SD2) comes from the factory selected as device number 8, drive number 0 and 1. This is the usual or "default" device number, but if more than one disk drive is to be used with the system, it is necessary to give each disk drive a different device number or drive number. With this disk drive, it is not possible to change the drive numbers (ie 0 and 1), but the device number can be changed using either software (a short BASIC program after power up) or hardware (changing jumpers on the drive PC board). The disk drive determines its device number from a set of jumpers on the PC board inside the drive. At the time the drive is powered on, the jumper settings are "read" by the microprocessor and the resulting number is stored in a specific memory location. This makes it possible to change the default device number by changing (opening or closing) the jumpers. After power up, the device number can be changed by using a "memory-write" command to the memory location that has the device number stored in it. That command must be used each time the drive is turned on. Each method has advantages and disadvantages which will be detailed below. CHANGING THE DEVICE NUMBER BY THE JUMPER (HARDWARE METHOD) 1. Turn off the drive and remove all cables from the drive. 2. Remove six screws from the drive case and remove the top cover. 3. Locate the jumper block JB1 on the top of the PC board near the rear of the drive. It is located between ICs U10 and U11. At that location, there are four solder pads with two bare wire "jumpers" soldered in horizontally. This is the factory configuration for device 8. If JB1-1 is cut (or simply unplugged if a "header" with a removable jumper is installed), the drive will respond as device 9 when powered up. If the jumper at JB1-2 is removed, the drive will be device 10, and with both jumpers removed, device 11. A SPST (single pole, single pole) switch can be installed instead of a jumper to allow the drive to be changed later without opening the case. Note: there is room on the rear of the case for added switches. 4. Replace the case top and install the cabinet screws. Electrically, the two jumpers ground two pins of an IC, namely U22 buffer (74LS240) pins 11 and 17. With a jumper at JB1-1, pin 17 of U22 is grounded, and with a jumper at UB1-2, pin 11 is grounded. This info is helpful in case the solder pads or board traces become damaged and cannot be used. CHANGING THE DEVICE NUMBER BY SOFTWARE The device number can be changed by performing a memory-write to locations $0077 and $0078. The memory-write command is performed after the command channel has been opened with a BASIC statement, usually: OPEN 15,8,15 The memory-write has the following format: PRINT#