Specifications

MSM800XEV/XEL / Detailed System Description
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6.8.5 Speaker Interface
One of the board's CPU devices provides the logic for a PC compatible speaker port. The speaker logic signal is
buffered by a transistor amplifier, and provides approximately 0.1 Watt of audio power to an external 8 Ohm speaker.
Connect the speaker between VCC and speaker output to have no quiescent current.
6.9 Controllers
6.9.1 Interrupt Controllers
An 8259A compatible interrupt controller, within the chipset, provides seven prioritized interrupt levels. Of these,
several are normally associated with the board's onboard device interfaces and controllers, and several are available
on the AT expansion bus.
Interrupt Sources Used Onboard
IRQ0 ROM-BIOS clock tick function, from timer 0 yes
IRQ1 Keyboard controller output buffer full yes
IRQ2 Used for cascade 2. 8259 yes
IRQ3 COM2 serial port yes
IRQ4 COM1 serial port yes
IRQ5 LPT2 parallel printer (if present) no 
IRQ6 Floppy controller yes
IRQ7 LPT1 parallel printer yes
IRQ8 Battery backed clock yes
IRQ9 Free for user no 
IRQ10 Free for user no 
IRQ11 Free for user no 
IRQ12 PS/2 mouse yes
IRQ13 Math. coprocessor yes
IRQ14 Hard disk IDE yes
IRQ15 Free for user no 
 May depend on the LAN configuration.
6.10 Timers and Counters
6.10.1 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 1.190MHz
clock, derived from a 14.318MHz 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 (18.2Hz)
1 DRAM refresh request timing (15µs)
2 Speaker tone generation time base