
W83877ATF
Publication Release Date: April 1998
- 151 -
Version 0.51
8.3.1 SMI to SCI/SCI to SMI and Bus Master
For the process of generating an interrupt from SMI to SCI or from SCI to SMI, see the following
figure for an illustration.
BIOS_RLS
GBL_EN
from SCI to SMI
GBL_RLS
BIOS_EN
Bus Master SCI
BM_CNTPL
BM_RLD
clear
set
BM_STS
To SCI Logic
To SMI Logic
To SCI Logic
from SMI to SCI
clear
set
clear
set
GBL_STS
BIOS_STS
: Status bit
: Enable bit
For the BIOS software to raise an event to the ACPI software, BIOS_RLS, GBL_EN, and GBL_STS
bits are involved. GBL_EN is the enable bit and the GBL_STS is the status bit. Both are controlled by
the ACPI software. If BIOS_RLS is set by the BIOS software and GBL_EN is set by the ACPI
software, an SCI interrupt is raised. Writing a 1 to BIOS_RLS sets it to logic 1 and also sets
GBL_STS to logic 1; Writing a 0 to BIOS_RLS has no effect. Writing a 1 to GBL_STS clears it to
logic 0 and also clears BIOS_RLS to logic 0; writing a 0 to GBL_STS has no effect.
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