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Interval Timers
The voltage regulator has three counters that are typically programmed to
provide the following functions:
Real-Time Clock and NVRAM
The real-time clock provides a century calendar, as well as a time-of-day
function. In addition, 256 bytes of battery-backed RAM is available for use
by the BIOS. A separate 3 V coin cell battery provides battery-backup.
BIOS
The VP22 supports the Intel 82802BA Firmware Hub (FWH). A boot
block device allows recovery of the BIOS in the event of a catastrophic
failure (power fail during BIOS update). Flash write protection is
implemented under software control and this bit must be set to 1 before any
write is allowed to the BIOS Flash. For more information on the VP22
motherboard's BIOS, refer to the VP22 microATX Motherboard BIOS and
Programmer's Reference Guide, listed in
Documentation.
Audio Interface
The VP22 provides a two channel, multimedia audio device capable of
Audio Codec '97 (AC '97). Three connectors are available on the rear
panel: MIC IN, LINE IN and LINE OUT.
http://www.motorola.com/computer/literature
Counter 0 is associated with IRQ0 and can be used for system
timing functions, such as timer interrupt for a time-of-day.
Counter 1 is used to generate a refresh request signal for ISA
memory every 15.6 us.
Counter 2 is typically programmed to provide a speaker tone.
Interval Timers
Appendix C, Related
2
2-7
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