I finally removed the BOOT ROM chip from the SORD M68 board.
The BOOT ROM chip is Toshiba's TMM333P. This chip has a different pin layout than the major 2732 and 2764 ROMs, so it cannot be read with my ROM writer.
So I used the Arduino Mega2560 to read the data in the TMM333P.
Now that I have the boot program in binary format, the first thing I need to do is to find out the address of the serial port.
The serial I/O function of SORD M68 is realized by two Z80SIO/2s. Z80SIO has many variations of initialization code due to its multiple functions, making analysis difficult.
On analysis, it is impossible to tell whether this discovered port address is port A or port B. However, it doesn't really matter if we don't know, so for convenience, we set the first discovered port address as port A and the next as port B.
SIOA Data Register : 0xF8 (not yet determined)
SIOA Control Register : 0xF9
SIOB Data Register : 0xFA (not yet determined)
SIOB Control Register : 0xFB
Setting: 8 bits, no parity, 2 stop bits, x16 (specific baud rate unknown), but SIOB setting is undetermined
