Troubleshooting
6-80
CSA7404B, TDS7704B, TDS7404B, TDS7254B & TDS7154B Service Manual
Table 6- 9: POST codes (Cont.)
Displayed
error code
Error message
Displayed
error code
Error message
4Bh Amount of memory above 1M f ound and verified. (If
power on, go to check point 4Eh).
D4h Verify base memory.
4Ch Memory below 1M cleared. (SOFT RESET) D5h Copy initialization code to segment 0 and transfer
control to segment 0.
4Dh Memory above 1M cleared. (SOFT RESET) Going
to save the memory size. (Go to check
point # 52h).
D6h Control is in segment 0. To check recovery mode
and verify main BIOS checksum. If either it is
recovery mode or the main BIOS checksum is bad,
go to check point E0 f or recovery, else go to check
point D7 for giving control to main BIOS.
4Eh Memory test started. (NOT SOFT RESET) D7h Find Main BIOS module in ROM image.
4Fh Memory size display started. Thi s will be updated
during memory test. Going for sequential and
random memory test.
D8h Uncompress the main BIOS module.
50h Memory testing/initialization below 1M complete. D9h Copy main BIOS image to F000 shadow RAM and
give control to main BIOS in F000 shadow RAM.
51h Memory size display adjusted due to relocati on/
shadow.
E0h On-board Floppy Controller is initialized. Com-
pressed recovery code is uncompressed in
F000:0000 in Shadow RAM and give control to
recovery code in F000 Shadow RAM. Init ialize
interrupt vector tables, initialize syst em tim er,
initialize DMA controller and interrupt controller.
52h Memory testing/initialization above 1M complet e. E8h Initialize extra (Intel Recovery) Module.
53h Memory size information is saved. CPU registers
are saved.
E9h Initialize floppy drive.
54h Shutdown successful, CPU in real mode. EAh Try to boot from floppy. If reading of boot sector is
successful, give control t o boot sector code.
57h A20 address line, parity/NMI disable successf ul. EBh Booting from floppy failed, look for ATAPI (LS-120,
Zip) devices.
58h Memory size adjusted for relocation/shadow. ECh Try to boot from ATAPI. If reading of boot sector is
successful, give control t o boot sector code.
59h Hit <DEL> message cleared. <WAIT .> message
displayed.
EFh Booting from floppy and ATAPI device failed. Give
two beeps. Retry the booting procedure again; go
to check point E9).
60h DMA page register test passed.
While control is inside the different bus routines, additional checkpoints are
output to port 80h to identify the routines. In these checkpoints, the low byte of
the checkpoint is the system BIOS checkpoint from which the control is passed
to the different bus routines. The high byte of the checkpoint indicates which
routine is being executed. Table 6--10 describes which function being executed.
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