82371AB Datasheet, PDF (150/284 Pages) Intel Corporation – PCI-TO-ISA / IDE XCELERATOR PIIX4

82371AB (PIIX4)
E
7.3.3. SMBHSTCNT—SMBUS HOST CONTROL REGISTER (IO)
I/O Address:
Default Value:
Attribute:
Base + (02h)
00h
Read/Write
The control register is used to enable SMBus controller host interface functions. Reads to this register clears the
host interface’s index pointer to the block data storage array.
Bit
Description
7 Reserved.
6 Start (START)—R/W. 1=Start execution. Writing a 1 to this bit initiates the SMBus controller host
interface to execute the command programmed in the SMB_CMD_PORT field. All necessary
registers should be setup prior to writing a 1 to this bit position. 0=Writing a 0 has no effect. This bit
always reads 0. The HOST_BUSY bit can be used to identify when the SMBus host controller has
finished executing the command.
5 Reserved.
4:2 SMBus Command Protocol (SMB_CMD_PROT)—R/W. Selects the type of command the SMBus
controller host interface will execute. Reads or writes are determined by bit 0 of SMBHSTADD
register. This field is decoded as follows:
Bits[4:2]
000
001
010
011
Protocol
Quick Read or Write
Byte Read or Write
Byte Data Read or Write
Word Data Read or Write
Bits[4:2]
100
101
110
111
Protocol
Reserved
Block Read or Write
Reserved
Reserved
1 Kill (KILL)—R/W. 1=Stop the current in process SMBus controller host transaction. This sets the
FAILED status bit and asserts the interrupt selected by the SMB_INTRSEL field. 0=Allows the
SMBus controller host interface to function normally.
0 Interrupt Enable (INTEREN)—R/W. 1=Enable the generation of interrupts (IRQ9OUT) on the
completion of the current host transaction. 0=Disable.
7.3.4. SMBHSTCMD—SMBUS HOST COMMAND REGISTER (IO)
I/O Address:
Default Value:
Attribute:
Base + (03h)
00h
Read/Write
This register is transmitted by the SMBus controller host interface in the command field of the SMBus protocol.
Bit
Description
7:0 SMBus Host Command (HST_CMD)—R/W. This field contains the data transmitted in the
command field of SMBus host transaction.
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