Mitsubishi Electric Apricot Owner's Handbook Manual page 157

T e c h n i c a l I n f o r m a t i o n
I/O Map
I/O Address
0800h : write
2
0120h : write
0120h : read
0121h : write
0122h : r/w
0123h 0127h
0128h 012Fh
03E8h 03EFh
02E8h 02EFh
= Unused portion of memory
Port 80 Monitor : 0080h : write
This 8-bit port captures all diagnostic codes written by the motherboard
BIOS. The port is readable by DiagP, which can then communicate the
codes to the SMC. If the port contents are lost due to overrun by the
motherboard, there is no problem; the aim is merely to keep track of the
last value in the event that the system hangs.
When the port is written, the DiagP must be informed through an
interrupt line (PORT80_IRQ).
When the DiagP reads the port, the interrupt line must be automatically
reset.
5-42 OWNER'S HANDBOOK
Port
Port 80 Diagnostic Port
BIOS page register
Status register
DOS Flash page register
Control register
Reserved for expansion
Diagnostic UART
COM3
COM4