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5.2 Intel ICH6-M South Bridge(1)
PCI Interface Signals
Name Type Description
AD[31:0]
I/O PCI Address/Data: AD[31:0] is a multiplexed address and data bus.
During the first clock of a transaction, AD[31:0] contain a physical
address (32 bits). During subsequent clocks, AD[31:0] contain data.
The Intel® ICH6 will drive all 0s on AD[31:0] during the address
phase of all PCI Special Cycles.
C/BE[3:0]#
I/O Bus Command and Byte Enables: The command and byte enable
signals are multiplexed on the same PCI pins. During the address
phase of a transaction,
C/BE[3:0]# define the bus command. During the data phase
C/BE[3:0]# define the Byte Enables.
C/BE[3:0]# Command Type
0000b Interrupt Acknowledge
0001b Special Cycle
0010b I/O Read
0011b I/O Write
0110b Memory Read
0111b Memory Write
1010b Configuration Read
1011b Configuration Write
1100b Memory Read Multiple
1110b Memory Read Line
1111b Memory Write and Invalidate
All command encodings not shown are reserved. The ICH6 does not
decode reserved values, and therefore will not respond if a PCI master
generates a cycle using one of the reserved values.
DEVSEL#
I/O Device Select: The ICH6 asserts DEVSEL# to claim a PCI
transaction. As an output, the ICH6 asserts DEVSEL# when a PCI
master peripheral attempts an access to an internal ICH6 address or an
address destined DMI (main memory or graphics). As an input,
DEVSEL# indicates the response to an ICH6-initiated transaction on
the PCI bus. DEVSEL# is tri-stated from the leading edge of
PLTRST#. DEVSEL# remains tri-stated by the ICH6 until driven by
a target device.
FRAME#
I/O Cycle Frame: The current initiator drives FRAME# to indicate the
beginning and duration of a PCI transaction. While the initiator
asserts FRAME#, data transfers continue. When the initiator negates
FRAME#, the transaction is in the final data phase. FRAME# is an
input to the ICH6 when the ICH6 is the target, and FRAME# is an
output from the ICH6 when the ICH6 is the initiator. FRAME#
remains tri-stated by the ICH6 until driven by an initiator.
PCI Interface Signals (Continued)
Name Type Description
IRDY#
I/O Initiator Ready: IRDY# indicates the ICH6's ability, as an initiator,
to complete the current data phase of the transaction. It is used in
conjunction with TRDY#. A data phase is completed on any clock
both IRDY# and TRDY# are sampled asserted. During a write,
IRDY# indicates the ICH6 has valid data present on AD[31:0].
During a read, it indicates the ICH6 is prepared to latch data. IRDY#
is an input to the ICH6 when the ICH6 is the target and an output
from the ICH6 when the ICH6 is an initiator. IRDY# remains
tri-stated by the ICH6 until driven by an initiator.
TRDY#
I/O Target Ready: TRDY# indicates the ICH6's ability as a target to
complete the current data phase of the transaction. TRDY# is used in
conjunction with IRDY#. A data phase is completed when both
TRDY# and IRDY# are sampled asserted.
During a read, TRDY# indicates that the ICH6, as a target, has placed
valid data on AD[31:0]. During a write, TRDY# indicates the ICH6,
as a target is prepared to latch data. TRDY# is an input to the ICH6
when the ICH6 is the initiator and an output from the ICH6 when the
ICH6 is a target. TRDY# is tri-stated from the leading edge of
PLTRST#. TRDY# remains tri-stated by the ICH6 until driven by a
target.
STOP#
I/O Stop: STOP# indicates that the ICH6, as a target, is requesting the
initiator to stop the current transaction. STOP# causes the ICH6, as an
initiator, to stop the current transaction. STOP# is an output when the
ICH6 is a target and an input when the ICH6 is an initiator.
PAR
I/O Calculated/Checked Parity: PAR uses “even” parity calculated on
36 bits, AD[31:0] plus C/BE[3:0]#. “Even” parity means that the
ICH6 counts the number of one within the 36 bits plus PAR and the
sum is always even. The ICH6 always calculates PAR on 36 bits
regardless of the valid byte enables. The ICH6 generates PAR for
address and data phases and only guarantees PAR to be valid one PCI
clock after the corresponding address or data phase. The ICH6 drives
and tri-states PAR identically to the AD[31:0] lines except that the
ICH6 delays PAR by exactly one PCI clock. PAR is an output during
the address phase (delayed one clock) for all ICH6 initiated
transactions. PAR is an output during the data phase (delayed one
clock) when the ICH6 is the initiator of a PCI write transaction, and
when it is the target of a read transaction. ICH6 checks parity when it
is the target of a PCI write transaction. If a parity error is detected, the
ICH6 will set the appropriate internal status bits, and has the option to
generate an NMI# or SMI#.
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