- I've just uploaded an improved version of the MBL EPROM code in Files>8800 EPROM Images. This new version does the following: 1) replace the 88-HSR code with code that allows you to load from the 88-2SIO 2nd port. (This allows you to load from an RS-232 high-speed paper tape reader on the 2nd 88-2SIO port, while your console is on the 1st port.) 2) Set the stop bits correctly for the 1st 88-2SIO port, according to the sense switch settings. (The MITS code always set it for 2 stop bits, regardless of the sense switches.) 3) Initialize both the 88-PIO and 88-4PIO correctly for devices like the OP-80 paper tape reader.
I also uploaded my own disassembled & commented version of the MITS MBL image, which explains the initialization code, among other things.