In the previous post I wrote about the new loader program I made. I use the speed of 300 baud. But how I get this. In this post I will explane more about this.
In my storage I have some older computers, also with W98 installed. They have also an real comport. So I took one of these PC’s, install the Z80 assembly and loader program on it and do my tests. This works good. I took my logicanalyser, a kind of USBee AX. I upload a little program to the MPF-1b and look with this analyser to the signals. With the USBee you can also do some protocol analyse. We know this is an “old” system, so we have low-speed communication. 1200 baud or lower. So we choose one and test. With this tool I found the communication setting of 300 8N1.
In the protocol analyse tool from the USBee AX you can see exact the same value as in the old loader program. So in this case we know we have the right settings.
With the information of this test we made the new loader program.