W83977ATF Datasheet, PDF (171/207 Pages) Winbond – WINBOND I/O

W83977ATF
PRELIMINARY
For the ACPI software to raise an event to the BIOS software, GBL_RLS, BIOS_EN, and BIOS_STS
bits are involved. BIOS_EN is the enable bit and the BIOS_STS is the status bit. Both are controlled
by the BIOS software. If GBL_RLS is set by the ACPI software and BIOS_EN is set by the BIOS
software, an SMI is raised. Writing a 1 to GBL_RLS sets it to logic 1 and also sets BIOS_STS to
logic 1. Writing a 0 to GBL_RLS has no effect. Writing a 1 to BIOS_STS clears it to logic 0 and also
clears GBL_RLS to logic 0. Writing a 0 to BIOS_STS has no effect.
For the bus master to raise an event to the ACPI software, BM_CNTRL, BM_RLD, and BM_STS bits
are involved. Both BM_RLD and BM_STS are controlled by the ACPI software. If BM_CNTRL is set
by the BIOS software and BM_RLD is set by the ACPI software, an SCI interrupt is raised. Writing a
1 to BM_CNTRL sets it to logic 1 and also sets BM_STS to logic 1. Writing a 0 to BM_CNTRL has no
effect. Writing a 1 to BM_STS clears it to logic 0 and also clears BM_CNTRL to logic 0. Writing a 0
to BM_STS has no effect.
9.2 Power Management Timer
In the ACPI specification, a power management timer is required. The power management timer is a
24-bit fixed rate free running up-count timer that runs off a 3.579545MHZ clock. The power
management timer corresponds to status bit (TMR_STS) and enable bit (TMR_EN). The TMR_STS
bit is set any time the last bit of the timer (bit 23) goes from 0 to 1 or from 1 to 0. If the TMR_EN bit
is set, the setting of the TMR_STS bit will generate an SCI interrupt. Three registers are used to
read the timer value which are located in the PM1 register block. The power management timer has
one enable bit (TMR_ON) to turn it on or off. The TMR_ON is located in GPE register block. If it is
cleared to 0, the power management timer function will not work. There are no timer reset
requirements, except that the timer should function after power-up. See the following figure for
illustration.
-115 -
Publication Release Date:April 1998
Revision 0.53