I got a monochrome monitor out of storage, and unsurprisingly, it shows the Sol-20 video much more clearly than the color TV did.
I hooked up the serial port of the Sol-20 to a null modem adapter and USB-to-serial adapter plugged into my laptop. The first thing I discovered is that the Sol wouldn’t accept the Solos “SET I=1″ or “SET O=1″ commands to set the input or output to use the serial port. It didn’t seem to accept any SET commands at all. Probably the personality module has a modified version of Solos with a disk bootstrap.
I have five simple personality modules: two PM-5204, two PM-2708, and one from Golemics with two 2708 EPROMs. I also have a dual personality module from Micro Complex, which has a switch to select between two sockets, which, provided that the Sol has a modification installed, result in one selection being mapped at C000, and the other at F000. The modification moves the Sol’s video RAM and scratch RAM in that block also, so in the F000 position, it provides for 60K of contiguous usable RAM. The F000 ROM may also be modified to support the Micro Complex 80×24 display daughterboard. Jim Battle’s excellent Sol20.org has a PDF of the manual for the dual personality module, as well as the source code and hexadecimal image of the Micro Complex ROM.
I’ve taken photos of the six personality modules.
The Micro Complex personality module appears to be the only one I have with a standard Solos image; it has the Processor Technology masked ROM in the C000 position. I’m currently using the Sol that does not have the 80×24 display daughterboard, nor the modification to relocate the C block to F, but using it with the C setting works and gives me the standard Solos, so I can use the SET I and O commands. Now I can download code into the Sol over the serial port from the laptop.
>I hooked up the serial port of the Sol-20 to a null modem adapter and USB-to-serial adapter plugged into my laptop. The first thing I discovered is that the Sol wouldn’t accept the Solos “SET I=1? or “SET O=1? commands to set the input or output to use the serial port. It didn’t seem to accept any SET commands at all. Probably the personality module has a modified version of Solos with a disk bootstrap.
Or perhaps it’s selective with which serial devices it interfaces. USB parallel and serial adapters, being USB packet based, are inherently broken for timing sensitive operation.
It’s just ordinary serial with no special timing requirements.