82371AB (PIIX4)
E
86
4/9/97 2:23 PM PIIX4aDS
INTEL CONFIDENTIAL
(until publication date)
PRELIMINARY
4.2.6.
ADVANCED POWER MANAGEMENT (APM) REGISTERS
This section describes two power management registers—APMC and APMS Registers. These registers are
located in normal I/O space and must be accessed (via the PCI Bus) with 8-bit accesses.
4.2.6.1.
APMC—Advanced Power Management Control Port (IO)
I/O Address:
Default Value:
Attribute:
0B2h
00h
Read/Write
This register passes data (APM Commands) between the OS and the SMI handler. In addition, writes can
generate an SMI. PIIX4 operation is not affected by the data in this register.
Bit
Description
7:0
APM Control Port (APMC).
Writes to this register store data in the APMC Register and reads return
the last data written. In addition, writes generate an SMI, if the APMC_EN bit (PCI function 3, offset
58h, bit 25) is set to 1. Reads do not generate an SMI.
4.2.6.2.
APMS—Advanced Power Management Status Port (IO)
I/O Address:
Default Value:
Attribute:
0B3h
00h
Read/Write
This register passes status information between the OS and the SMI handler. PIIX4 operation is not affected by
the data in this register.
Bit
Description
7:0
APM Status Port (APMS).
Writes store data in this register and reads return the last data written.
4.2.7.
X-BUS, COPROCESSOR, AND RESET REGISTERS
4.2.7.1.
RIRQ—Reset X-Bus IRQ12/M and IRQ1 Register (IO)
I/O Address:
Default Value:
Attribute:
60h
N/A
Read only
This register clears the mouse interrupt function (IRQ12/M) and the keyboard interrupt (IRQ1). Reads and writes
to this address are accepted by PIIX4 and sent to ISA (Keyboard accesses must be enabled if in Positive
decode). PIIX4 latches low to high transitions on IRQ1 and IRQ12/M (when enabled as mouse interrupt). A read
of 60h clears the internally latched signals of IRQ1 and IRQ12/M.
Bit
Description
7:0
Reset IRQ12 and IRQ1.
No specific pattern. A read of address 60h clears the internally latched
IRQ1 and IRQ12/M signals.