2.4 System Board Troubleshooting 2 Troubleshooting Procedures
5. Execute GETDPORT.COM in the text menu in CPU REAL mode. (Insert the FD for
starting D port into FDD and input “FD starting drive:>dport”.)
The D port status is displayed in the following form;
6. When the D port status is FFFFh (normal status), go to Procedure 3.
7. When the D port status falls into any status in Table 2-4, execute Check 1.
Table 2-4 Debug port error status (1/7)
D port status Inspection items Details
F000h Clear of software reset bit
Permission of A20 line
Initialization of special register and M1535
PIT CH0 initialization (for HOLD_ON)
BIOS rewrite factor flag initialization
Check sum check (FEFC0000h-FEFF7FFFh)
Transition to protected mode
Boot block checksum Program halt when check sum error
Checksum other than boot block
F001h EC/KBC rewrite check BIOS rewrite process when rewrite is
requested
KBC initialization sequence
Send KB Enables command.
Check F12 key
F002h Initialization of security controller
F003h
-F005h BIOS rewrite request check Check sum error except BootBlock
when “F12 rewrite” is requested
F006h BIOS signature check
F007h BIOS rewrite process
Transition to System BIOS IRT
BIOS rewrite Initialization of H/W of unique function
for each model
Initialization of I/O space for GPIO
Permission of BIOS writing
Serial interrupt control
2-22 PORTEGE M300 Maintenance Manual (960-504)