Advantech SOM-Express Design Guide
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Chapter 5 Carrier Board Design Guidelines
Chapter 5 Carrier Board Design Guidelines
5.1 PCI-Bus
SOM-Express provides a PCI Bus interface that is compliant with the PCI Local Bus
Specification, Revision 2.3. The implementation is optimized for high-performance
data streaming when SOM-Express is acting as either the target or the initiator on the
PCI bus. For more information on the PCI Bus interface, please refer to the PCI Local
Bus Specification, Revision 2.3.
5.1.1 Signal Description
Table 5-1 shows SOM-Express PCI bus signal, including pin number, signals, I/0,
and descriptions.
Table 5.1 PCI Signal Description
Pin Signal
I/O
Description
D50
PCI_CLK
O
PCI 33 MHz clock output
D48 PCI_CLKRUN#
I/O
Bidirectional pin used to support PCI clock run protocol for
mobile systems
C22,C19,
C17,D20
PCI_REQ[0..3] I
Bus Request signals for up to 4 external bus mastering PCI
devices. When asserted, a PCI device is requesting PCI bus
ownership from the arbiter.
C20,C18,
C16,D19
PCI_GNT[0..3] O
Grant signals to PCI Masters. When asserted by the arbiter, the
PCI master has been granted ownership of the PCI bus.
- PCI_AD[0..31]
I/O
PCI Address and Data Bus Lines. These lines carry the address
and data information for PCI transactions.
D26,C33,
C38,C44
PCI_C/BE[0..3] I/O
PCI Bus Command and Byte Enables. Bus command and byte
enables are multiplexed in these lines for address and data
phases, respectively.
D32
PCI_PAR
I/O
Parity bit for the PCI bus.
D33 PCI_SERR#
I/O
OD
System Error. Asserted for hardware error conditions such as
parity errors detected in DRAM.
C34 PCI_PERR# I/O
Parity Error. For PCI operation per exception granted by PCI 2.1
Specification.
C15
PME#
I
Power management event.
C35
PCI_LOCK#
I/O
Lock Resource Signal. This pin indicates that either the PCI
master or the bridge intends to run exclusive transfers.
C36 PCI_DEVSEL#
I/O
Device Select, active low. When the target device has decoded
the address as its own cycle, it will assert DEVSEL#.
D35
PCI_TRDY#
I/O
Target Ready. This pin indicates that the target is ready to
complete the current data phase of a transaction.
C37
PCI_IRDY#
I/O
Initiator Ready. This signal indicates that the initiator is ready to
complete the current data phase of a transaction.
D34
PCI_STOP#
I/O
Stop. This signal indicates that the target is requesting that the
master stop the current transaction.
D36
PCI_FRAME#
I/O
Cycle Frame of PCI Buses. This indicates the beginning and
duration of a PCI access.
C23
PCI_RESET#
I
PCI Bus Reset. This is an output signal to reset the entire PCI
Bus. This signal is asserted during system reset.
C49,C50,
D46,D47
PCI_IRQ[A…D]
I
PCI interrupt request lines.
D49 PCI_M66EN I
Module input signal indicates whether an off-module PCI device
is capable of 66 MHz operation. Pulled to GND by Carrier Board
device or by Slot Card if the devices are NOT capable of 66
MHz operation.
If the module is not capable of supporting 66 MHz PCI
operation, this input may be a no-connect on the module.
If the module is capable of supporting 66 MHz PCI operation,
and if this input is held low by the Carrier Board, the module PCI
interface shall operate at 33 MHz.
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