Capable of running FreeDOS and text-based DOS programs. The BIOS resides in an in-system programmable EEPROM; the computer provides terminal-like text-based access via RS232 UART interface, and has an SD card based bootable permanent storage.

• CPU: 80C88-2, 5.5296 MHz
• RAM: 896 kB
• ROM: 128 kB
• I/O: 16C550 UART
• Storage: SD Card

The computer has no VGA adapter or keyboard interface, all interaction happens through the UART. In order to provide PC compatibility to text-based programs, INT 10h (VGA character out) and INT 16h (keyboard character in) BIOS calls are routed to the UART; this gives terminal-like access to text-based programs, like the FreeDOS shell.

The computer has a basic I/O port (4 bit in, 4 bit out), a virtual SPI interface is implemented on top of it through software (bit-banging). A daughter board with an SD card slot plugs directly into the I/O port socket and the BIOS implements SD card access routines on the virtual SPI interface.

On startup, the BIOS looks for an SD card on the SPI interface and searches for a valid MS-DOS partition on it. If a partition is found and has an exact size of 1.44MB, the computer can boot from it and the OS can read from and write to it via PC standard BIOS INT 13h calls, just as if it was an actual 1.44MB floppy disk.

The position-independent BIOS code can run from any 64k segment of the address space (even from RAM). Also, the BIOS provides routines for receiving 64k blocks via UART (e.g. a BIOS update), moving them around in the memory and burning them into the EEPROM - these features enable in-system EEPROM programming and development, without the need for an external EEPROM burner device.

https://sourcery.mentor.com/GNUToolchain/release3298

minipro -p SST39SF010A -w ./minipro.bin