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Technical training
Addresses for PC
Each internal peripheral of a computer is
characterized by an address (or rather a adress range) and an interruption. The
address of a peripheral (parallel port, serials, audio board, …) allows the
processor to communicate individualy with each the peripheral. This electronic
concept is similar to that of the postal address which makes it possible to
distinguish a correspondent.
IBM, the originator of the first PC standardized
certain addresses of peripherals. The first XT used only the interruptions from
0 to 7. The current computers allow more interrupt levels. Here the list of
these addresses standardized by IBM for the 286 and processors higher. Actual
computer use more levels.
Function
IRQ
Addresses into
hexadecimal
Comments
Clock system
0
Manage timings necessary to
the operation of the computer: cannot be modified
Keyboard
1
Cannot be modified
Controller of programmable
IRQ
2
Cannot be modified
COM 2
COM 4
3
2F8-2FF
2E8 - 2EF
Modifiable but
with incompatibility with certain old programs
COM 1
COM 3
4
3F8-3FF
3E8-3EF
Free
5
Generally used by the chart
its, also used according to the lassification of IBM by the port parralèle
LPT 2 with address $278
Controller Floppy drive
6
Modifiable but with
incompatibilities for the old ones programs (the disk drives are not
established any more on the current machines)
LPT 1
LPT 2
7
378.-37F (3C for certain
computers of mark)
278 - 27F
Modifiable with prudence. One
can put parallel ports LPT1 and LPT2 on the same interruption, but not
of simultaneous impressions
Clock (RTC): date and hour
8
Not to modify
9
Free starting from Pentium
(that dates) and following, used in parallel with IRQ2 as connection in
processors 486. Often recovered by the audio charts.
