Toshiba PORTEGE M300 Maintenance Manual page 71

2.4 System Board Troubleshooting
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.
D port status
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
Transition to protected mode
Boot block checksum
Checksum other than boot block
F001h EC/KBC rewrite check
KBC initialization sequence
Send KB Enables command.
Check F12 key
F002h Initialization of security controller
F003h BIOS rewrite request check
-F005h
F006h BIOS signature check
F007h BIOS rewrite process
Transition to System BIOS IRT
BIOS rewrite
2-22
Table 2-4 Debug port error status (1/7)
Inspection items
2 Troubleshooting Procedures
Details
(FEFC0000h-FEFF7FFFh)
Program halt when check sum error
BIOS rewrite process when rewrite is
requested
Check sum error except BootBlock
when "F12 rewrite" is requested
Initialization of H/W of unique function
for each model
Initialization of I/O space for GPIO
Permission of BIOS writing
Serial interrupt control
PORTEGE M300 Maintenance Manual (960-504)