Someone was kind enough to mail me the masked ROM out of his HP 9895 floppy drive. I've read it and mailed it back. It's an MK36000 series 24-pin 8KB masked ROM, with the same pinout as the Motorola MC68764 EPROM, so reading it with an EPROM programmer set for the Motorola part should work fine. In read mode, no programming voltage is applied, so there should be no risk of damage to the part. Unfortunately my Data I/O Unisite does too good a job trying to protect devices against reverse or misaligned insertion or incorrect device configuration; if it thinks the current drawn by the device is too low or too high, it aborts with a device insertion error. The MK36000 draws significantly less current than the MCM68764. I tried putting an appropriately valued resistor in parallel, but still got the error.
I ended up kludging the masked ROM to the expansion bus interface of a TI Launchpad board with a Tiva TM4C1294 microcontroller (ARM Cortex-M4 based), using an SN74LVC245A buffer on the data bus because the Tiva is not 5V-tolerant. I wrote C code to read the ROM and send a hex dump out the USB-serial interface. Photo: https://www.flickr.com/photos/22368471@N04/21611518545/ As I've needed to use the expansion bus interface of the Tiva for other projects, even though this was a lot of work to read one ROM, the experience and maybe even the code may be useful in the future. The next issue is that it appears that the 9895 may permute the address and/or data busses, as the contents of the ROM don't actually look like reasonable Z80 code.
