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PCI Interface Signals (Continued)
Signal Name
Type
Description
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 ICH4 when the ICH4 is the Target, and
FRAME# is an output from the ICH4 when the ICH4 is the Initiator.
FRAME# remains tri- stated by the ICH4 until driven by an
Initiator.
IRDY#
I/O
Initiator Ready:
IRDY# indicates the ICH4'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 that both IRDY# and TRDY# are sampled asserted. During a
write, IRDY# indicates the ICH4 has valid data present on
AD[31:0]. During a read, it indicates the ICH4 is prepared to latch
data. IRDY# is an input to the ICH4 when the ICH4 is the Target
and an output from the ICH4 when the ICH4 is an Initiator. IRDY#
remains tri-stated by the ICH4 until driven by an Initiator.
TRDY#
I/O
Target Ready:
TRDY# indicates the ICH4'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 ICH4, as a Target, has
placed valid data on AD[31:0]. During a write, TRDY# indicates
that the ICH4, as a Target, is prepared to latch data. TRDY# is an
input to the ICH4 when the ICH4 is the Initiator and an output from
the ICH4 when the ICH4 is a Target. TRDY# is tri-stated from the
leading edge of PCIRST#. TRDY# remains tri-stated by the ICH4
until driven by a target.
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
ICH4 counts the number of 1s within the 36 bits plus PAR and the
sum is always even. The ICH4 always calculates PAR on 36 bits
regardless of the valid byte enables. The ICH4 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 ICH4
drives and tri-states PAR identically to the AD[31:0] lines except
that the ICH4 delays PAR by exactly one PCI clock. PAR is an
output during the address phase (delayed one clock) for all ICH4
initiated transactions. PAR is an output during the data phase
(delayed one clock) when the ICH4 is the Initiator of a PCI write
transaction, and when it is the Target of a read transaction. ICH4
checks parity when it is the Target of a PCI write transaction. If a
parity error is detected, the ICH4 will set the appropriate internal
status bits, and has the option to generate an NMI# or SMI#.
PCI Interface Signals (Continued)
Signal Name
Type
Description
STOP#
I/O
Stop:
STOP# indicates that the ICH4, as a Target, is requesting the
Initiator to stop the current transaction. STOP# causes the ICH4, as
an Initiator, to stop the current transaction. STOP# is an output
when the ICH4 is a Target and an input when the ICH4 is an
Initiator. STOP# is tri-stated from the leading edge of PCIRST#.
STOP# remains tri-stated until driven by the ICH4.
PERR#
I/O
Parity Error:
An external PCI device drives PERR# when it
receives data that has a parity error. The ICH4 drives PERR# when
it detects a parity error. The ICH4 can either generate an NMI# or
SMI# upon detecting a parity error (either detected internally or
reported via the PERR# signal).
REQ[4:0]#
REQ[5]#/
REQ[B]#/
GPIO[1]
I
PCI Requests:
The ICH4 supports up to 6 masters on the PCI bus.
REQ[5]# is muxed with PC/PCI REQ[B]# (must choose one or the
other, but not both). If not used for PCI or PC/PCI,
REQ[5]#/REQ[B]# can instead be used as GPIO[1].
NOTE:
REQ[0]# is programmable to have improved arbitration
latency for for supporting PCI-based 1394 controllers.
GNT[4:0]#
GNT[5]#/
GNT[B]#/
GPIO[17]
O
PCI Grants:
The ICH4 supports up to 6 masters on the PCI bus.
GNT[5]# is muxed with PC/PCI GNT[B]# (must choose one or the
other, but not both). If not needed for PCI or PC/PCI, GNT[5]# can
instead be used as a GPIO.
Pull-up resistors are not required on these signals. If pull-ups are
used, they should be tied to the Vcc3_3 power rail.
GNT[B]#/GNT[5]#/GPIO[17] has an internal pull-up.
PCICLK
I
PCI Clock:
This is a 33 MHz clock. PCICLK provides timing for
all transactions on the PCI Bus.
NOTE:
This clock does not stop based on STP_PCI# signal.
PCICLK only stops based on SLP_S1# or SLP_S3#.
PCIRST#
O
PCI Reset:
ICH4 asserts PCIRST# to reset devices that reside on
the PCI bus. The ICH4 asserts PCIRST# during power-up and when
S/W initiates a hard reset sequence through the RC (CF9h) register.
The ICH4 drives PCIRST# inactive a minimum of 1 ms after
PWROK is driven active. The ICH4 drives PCIRST# active
a minimum of 1 ms when initiated through the RC register.
PLOCK#
I/O
PCI Lock:
This signal indicates an exclusive bus operation and
may require multiple transactions to complete. ICH4 asserts
PLOCK# when it performs non- exclusive transactions on the PCI
bus. Devices on the PCI bus (other than the ICH4) are not permitted
to assert the PLOCK# signal.
SERR#
I/OD
System Error:
SERR# can be pulsed active by any PCI device that
detects a system error condition. Upon sampling SERR# active, the
ICH4 has the ability to generate an NMI, SMI#, or interrupt.
5.3 Intel 82801DBM I/O Controller Hub 4 Mobile (ICH4-M)(2)
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