DIGITAL-LOGIC AG PCCP5 Manual V2.3
135
The system BIOS gives control to the different BUSes at following check-points to performe vari-
ous tasks on the different BUSes.
CHECK-POINT DESCRIPTION OF CHECK-POINT
2A Different BUSes init (system, static, output devices) to
start if present.
38 Different BUSes init (input, IPL, general devices) to start
if present.
39 Display different BUSes initialization error messages.
95 Init of different BUSes optional ROMs from C800 to start.
While control is inside the different BUS routines, additional check-points are output to port 80h as
WORD to identify the routines under execution. These are WORD check-points, the LOW BYTE of
check-point is the system BIOS check-point from where the control is passed to the different BUS
routines and the HIGH BYTE of check-point is the indication of which routine is being executed in
different BUSes. The details of HIGH BYTE of these check-points are as follows:
HIGH BYTE XY
the upper nibble 'X' indicates the function# is being executed. 'X' can be
from 0 to 7.
0 = func#0, disable all devices on the BUS concerned.
1 = func#1, static devices init on the BUS concerned.
2 = func#2, output device init on the BUS concerned.
3 = func#3, input device init on the BUS concerned.
4 = func#4, IPL device init on the BUS concerned.
5 = func#5, general device init on the BUS concerned.
6 = func#6, error reporting for the BUS concerned.
7 = func#7, add-on ROM init 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 = Onboard System devices.
2 = ISA devices.
3 = EISA devices.
4 = ISA PnP devices.
5 = PCI devices.
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