Though I have complete description of the Cassette Interface PCBs, hooking those boards up to the main SCELBI chassis requires more research. One key to understanding this hookup, is understanding details of the software. The MEA software was written to work with some specific connections between the SCELBI I/O ports and cassette interface cards. With changes to the software, this could be done in a number off different ways. Since I want to run standard MEA software, I need to hook up the hardware to match the original configuration.

The cassette interface software driver resides in page 77 of a SCELBI set up with the MEA software. I have found two sources of this MEA cassette interface software driver. First is the hex file for page 77 of MEA that Cameron Cooper and Mark Arnold reconstructed. This file can be downloaded from scelbi.com. The other source is SCELBI Newsletter #3, which also can be found on scelbi.com. In order to figure out what the relationship between these two images is, I took the hex file of page 77 and disassembled it and then compared to the listing in the newsletter. It turns out that the two drivers appear to be identical. Since the newsletter listing, includes comments, it greatly helped the understanding of this driver.

While I’m not completely done investigating, I have been able to create a lightly commented source listing that can be assembled with my version of the AS8 assembler. Once I’m done investigating and have a cassette interface hooked up and working, I’ll be sure to post the description of the connections.

SCELBI Cassette Interface Source

SCELBI Cassette Inteface Assembly Listing

Stay tuned for an upcoming blog report, where I’ll describe what I did to create an 8008 disassembler, as well as post the source for it.