Controllers; Interrupt Controllers; Timers And Counters; Programmable Timers - DIGITAL-LOGIC Microspace MSM586SEN Technical User Manual

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4.4

Controllers

4.4.1

Interrupt Controllers

An 8259A compatible interrupt controller, within the ELAN520 chipset, provides seven prioritized interrupt
levels. Some of these IRQ's are normally associated with the board's onboard device interfaces and control-
lers, and several are available on the AT expansion bus.
Interrupt PIRQ
IRQ0
IRQ1 PIRQ1
IRQ2
IRQ3 PIRQ3
IRQ4 PIRQ4
IRQ5 PIRQ5
IRQ6 PIRQ6
IRQ7 PIRQ7
IRQ8 PIRQ8
IRQ9 PIRQ9
IRQ10 PIRQ10
IRQ11 PIRQ0
IRQ12 PIRQ2
IRQ13
IRQ14 PIRQ10
IRQ15 PIRQ8
* It may depends on the BIOS settings configuration
-
4.5

Timers and Counters

4.5.1

Programmable Timers

An 8253 compatible timer/counter device is also included in the board's ASIC device. This device is utilized
in precisely the same manner as in a standard AT implementation. Each channel of the 8253 is driven by a
1.190 MHz clock, derived from a 14.318 MHz oscillator, which can be internally divided in order to provide a
variety of frequencies.
Timer 2 can also be used as a general purpose timer if the speaker function is not required.
Timer Assignment
Timer Function
0 ROM-BIOS clock tick (18.2 Hz)
1 DRAM refresh request timing (15 µs)
2 Speaker tone generation time base
Sources:
ROM-BIOS clock tick function, from timer 0
Keyboard controller output buffer full
Used for cascade 2. 8259
COM2 serial port; (COM C or COM D)
COM1 serial port; (COM C or COM D)
Free for user; (COM C or COM D)
Floppy controller
LPT1 parallel printer; (COM C or COM D)
Battery backed clock
Free for user
Harddisk IDE
Free for user
PS/2 mouse
Math. coprocessor
Harddisk IDE
Free for user
(HIGH ACTIVE)
35
MSM586SEN/SEV Manual V1.5E
onboard used:
yes
yes
yes
yes
yes
(yes) *
yes
yes*
yes
no
yes *
no *
yes
yes
yes
no