BIOS Messages
ATXN-5520 / WTM7026 Technical Reference
Chassis Plans
A-12
Additional Checkpoints
While control is in the different functions, additional checkpoints are output to Port 80H as word values to
identify the routines being executed.
The low byte value indicates the main POST Code Checkpoint. The high byte is divided into two nibbles
and contains two sets of information. The details of the high byte of these checkpoints are detailed in the
following table:
High Byte XY
The upper nibble „X‟ indicates the function number that is being executed. „X‟ can be from 0 to 8.
0
Function 0. Disable all devices on the bus.
1
Function 1. Initialize static devices on the bus.
2
Function 2. Initialize output devices on the bus.
3
Function 3. Initialize input devices on the bus.
4
Function 4. Initialize IPL devices on the bus.
5
Function 5. Initialize general devices on the bus.
6
Function 6. Error reporting for the bus.
7
Function 7. Initialize add-on ROMs for all buses.
8
Function 8. Initialize BBS ROMs for all buses.
The lower nibble „Y‟ indicates the bus on which the different routines are being executed. „Y‟ can be from
0 to 5.
0
Generic DIM (Device Initialization Manager)
1
On-board system devices
2
ISA devices
3
EISA devices
4
ISA PnP devices
5
PCI devices
