The ROMs in the HX-20 are almost, but not exactly compatible with 2764 EPROMS. So my smart DATA IO programmer would not read them. But the HX-20 has a BASIC and a serial port, so a small program and a lot of patience will do the trick. It is simple and dumps only one ROM at the time. If you want another range, you have to change line 100.
Somehow I do not seem to get the HX-20 BASIC to calculate a proper checksum, boolean arithmetic is not present. Maybe I'll fix this later. The files below have a corrected checksum, so should be accepted by EPROM programmers.
The output format is currently Intel Intellec 8/MDS Format. The Motorola Exorciser (S1) Format would be more appropriate, but I leave this to the reader.
What you also need;
The download stuff:
Marco Orlandi send a ROM set dump of a HX-20 with a french keyboard.
Only the Monitor and Utility ROM differ.
An other tip is for reading these ROMs with a standard programmer. Connect pins 1,26,27,28 and setting CS
(chip select) to active high. Then the ROMS read as a Nec 2764. (Denis Kushch reports this is incorrect, just pins 28 and 26 should be connected, at least for the MiniPro EPROM programmer).
More ROMs:
Last update: 2023-07-22