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Stephan, How were you connecting the OSI to your host computer? This technique for RS-232 interfacing doesn't exactly use the correct voltage levels and may not work with all interfaces. I was using an USB to RS-232 converter. Do you have an oscilloscope? That could be a huge help. No, I don't have...

Klyball wrote:did you install the transistors or were they already in there, check that there in there correctly

I have installed the two transistors for the RS-232 interface myself, and yes, I had checked that they are installed correctly.

Klyball wrote:What revision is your board I'm pretty sure it makes a difference as to how it gets wired

It says "Ohio Scientific Model 600 CPU 1978 REV B" on the board.

Hi, in the past I had tried to implement the RS-232 interface to my Challenger 1P by following the instructions in "The first book of Ohio Scientifc Vol. I" and in the Professor Mark Csele: Ohio Scientific Computers web page. Unfortunately I never was able to make it work, and I abandoned the projec...

After Bill had kindly reminded me that the expansion board actually needs a power supply by bridging +5V to pin 11 of the expansion socket, the memoy expansion board now works!

Thanks, Bill, this is really great!

Stephan

So. I added the directories in my user folder, and the package compiled. I think that the powers-that-be need to remove that requirement. Not sure what exact version you built. I performed a build on a Mac OS X machine without problems. I don't want to hijack this thread with cc65 build issues, so ...

There doesn't seem to be a version there that will compile and run under Mac OS X, which is what I am using. I got as far as compiling a simple program using 2.13.3, but the linker cant find things like __STARTUP__ among others. I guess I am going to have to dig into the internal workings of it to ...

Hi Jeff, I am using the macro assembler that is part of this program: http://www.cc65.org I haven't figured out how to get the c compiler up and running yet, though. please note that http://www.cc65.org is outdated and no longer maintainted. The live page is http://cc65.github.io/cc65/ . From there ...

The relationship between the DD and R/W signal is not direct. To read (or write) from a device on the CPU (bus) side the 8T28, the DD signal will remain high at all times. However, to read from a device on the expansion (receiver/transmitter) side of the 8T28 the DD line must be driven low when the...

Hi, I'm following the projects for memory expansions, and I have some general questions about attaching memory or peripherals to the expansion socket on the 600 board. My quotes are referring to the 600revB manual . First of all, I found the description of the DD signal in the 600revB manual. On pag...