Toshiba A20-S259 Maintenance Manual - Page 73

2.12 Sound Troubleshooting 2 Troubleshooting Procedures Table 2-3 Printer port LED boot mode status (1/8) LED Status Test item FFh Start B0h Flash ROM check B1h EC/KBC rewrite check B2h BIOS rewrite check B3h System BIOS rewrite transition to IRT BIOS rewrite process Message Register initialization for boot block Clearing software reset bit Permitting A20 line Initialization of special register and Intel chip set PIT CH0 initialization (for HOLD ON) BIOS rewrite flag initialization Checksum check Transition to protected mode Boot block checksum check (The system halts when a checksum error is detected.) Transition to BIOS rewriting when rewrite is requested Executing KBC initialization sequence Enabling keyboard [Tilde], [TAB] key check BIOS rewrite request check when check sum error except for Boot Block is detected, or rewrite is requested by user Transition to BIOS rewrite System BIOS rewrite transition to IRT Hardware initialization Setting base for Power Management I/O Space Enabling BIOS write Special interrupt control Disabling BIOS write protect Enabling SMBus I/O space Enable SMBus access Opening work I/O for SDRAM initialization Setting FDC prohibition Hardware initialization for each model PIT CH1 initialization (setting refresh interval to 30 m/s) Initialization of PIT, DMAC, PIC Satellite A20 Maintenance Manual (960-444) 2-23