Intel 6 SERIES CHIPSET - DATASHEET 01-2011 Datasheet page 747

SMBus Controller Registers (D31:F3)
18.2.1 HST_STS—Host Status Register (SMBus—D31:F3)
Register Offset: SMB_BASE + 00h
Default Value:
All status bits are set by hardware and cleared by the software writing a one to the
particular bit position. Writing a 0 to any bit position has no effect.
Bit
7
6
5
4
3
2
Datasheet
00h
Byte Done Status (DS) — R/WC.
0 = Software can clear this by writing a 1 to it.
1 = Host controller received a byte (for Block Read commands) or if it has completed
transmission of a byte (for Block Write commands) when the 32-byte buffer is not
being used. Note that this bit will be set, even on the last byte of the transfer. This
bit is not set when transmission is due to the LAN interface heartbeat.
This bit has no meaning for block transfers when the 32-byte buffer is enabled.
NOTE: When the last byte of a block message is received, the host controller will set
this bit. However, it will not immediately set the INTR bit (bit 1 in this register).
When the interrupt handler clears the DS bit, the message is considered
complete, and the host controller will then set the INTR bit (and generate
another interrupt). Thus, for a block message of n bytes, the PCH will generate
n+1 interrupts. The interrupt handler needs to be implemented to handle these
cases. When not using the 32 Byte Buffer, hardware will drive the SMBCLK signal
low when the DS bit is set until SW clears the bit. This includes the last byte of a
transfer. Software must clear the DS bit before it can clear the BUSY bit.
INUSE_STS — R/W. This bit is used as semaphore among various independent
software threads that may need to use the PCH's SMBus logic, and has no other effect
on hardware.
0 = After a full PCI reset, a read to this bit returns a 0.
1 = After the first read, subsequent reads will return a 1. A write of a 1 to this bit will
reset the next read value to 0. Writing a 0 to this bit has no effect. Software can poll
this bit until it reads a 0, and will then own the usage of the host controller.
SMBALERT_STS — R/WC.
0 = Interrupt or SMI# was not generated by SMBALERT#. Software clears this bit by
writing a 1 to it.
1 = The source of the interrupt or SMI# was the SMBALERT# signal. This bit is only
cleared by software writing a 1 to the bit position or by RSMRST# going low.
If the signal is programmed as a GPIO, then this bit will never be set.
FAILED — R/WC.
0 = Software clears this bit by writing a 1 to it.
1 = The source of the interrupt or SMI# was a failed bus transaction. This bit is set in
response to the KILL bit being set to terminate the host transaction.
BUS_ERR — R/WC.
0 = Software clears this bit by writing a 1 to it.
1 = The source of the interrupt of SMI# was a transaction collision.
DEV_ERR — R/WC.
0 = Software clears this bit by writing a 1 to it. The PCH will then deassert the interrupt
or SMI#.
1 = The source of the interrupt or SMI# was due to one of the following:
• Invalid Command Field,
• Unclaimed Cycle (host initiated),
• Host Device Time-out Error.
Attribute: R/WC, RO
Size: 8-bits
Description
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