82801FB Datasheet, PDF (721/786 Pages) Intel Corporation – Intel I/O Controller Hub 6 (ICH6) Family

High Precision Event Timer Registers
20.1.6
TIMn_COMP—Timer n Comparator Value Register
Address Offset:
Attribute:
Default Value:
Timer 0: 108h–10Fh,
Timer 1: 128h–12Fh,
Timer 2: 148h–14Fh
R/W
N/A
Size:
64 bit
Bit
Description
Timer Compare Value — R/W. Reads to this register return the current value of the comparator
Timers 0, 1, or 2 are configured to non-periodic mode:
Writes to this register load the value against which the main counter should be compared for this
timer.
• When the main counter equals the value last written to this register, the corresponding
interrupt can be generated (if so enabled).
• The value in this register does not change based on the interrupt being generated.
Timer 0 is configured to periodic mode:
• When the main counter equals the value last written to this register, the corresponding
interrupt can be generated (if so enabled).
• After the main counter equals the value in this register, the value in this register is increased
by the value last written to the register.
63:0
For example, if the value written to the register is 00000123h, then
1. An interrupt will be generated when the main counter reaches 00000123h.
2. The value in this register will then be adjusted by the hardware to 00000246h.
3. Another interrupt will be generated when the main counter reaches 00000246h
4. The value in this register will then be adjusted by the hardware to 00000369h
• As each periodic interrupt occurs, the value in this register will increment. When the
incremented value is greater than the maximum value possible for this register (FFFFFFFFh
for a 32-bit timer or FFFFFFFFFFFFFFFFh for a 64-bit timer), the value will wrap around
through 0. For example, if the current value in a 32-bit timer is FFFF0000h and the last value
written to this register is 20000, then after the next interrupt the value will change to
00010000h
Default value for each timer is all 1s for the bits that are implemented. For example, a 32-bit timer
has a default value of 00000000FFFFFFFFh. A 64-bit timer has a default value of
FFFFFFFFFFFFFFFFh.
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Intel^® I/O Controller Hub 6 (ICH6) Family Datasheet
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