DIGITAL-LOGIC Microspace MSM586SEN - Controllers; Interrupt Controllers; Timers and Counters; Programmable Timers

DIGITAL-LOGIC AG MSM586SEN/SEV Manual V1.5E
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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 Sources: onboard used:
IRQ0 ROM-BIOS clock tick function, from timer 0 yes
IRQ1 PIRQ1 Keyboard controller output buffer full yes
IRQ2 Used for cascade 2. 8259 yes
IRQ3 PIRQ3 COM2 serial port; (COM C or COM D) yes
IRQ4 PIRQ4 COM1 serial port; (COM C or COM D) yes
IRQ5 PIRQ5 Free for user; (COM C or COM D) (yes) *
IRQ6 PIRQ6 Floppy controller yes
IRQ7 PIRQ7 LPT1 parallel printer; (COM C or COM D) yes*
IRQ8 PIRQ8 Battery backed clock yes
IRQ9 PIRQ9 Free for user no
IRQ10 PIRQ10
Harddisk IDE
yes *
IRQ11 PIRQ0 Free for user no *
IRQ12 PIRQ2 PS/2 mouse yes
IRQ13 Math. coprocessor yes
IRQ14 PIRQ10 Harddisk IDE yes
IRQ15 PIRQ8
Free for user (HIGH ACTIVE)
no
- * 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