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Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors—PCI Controller
Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
Develepor’s Manual
August 2006
528
Order Number: 306262-004US
interrupt to the Intel XScale processor. The PCI Controller provides no hardware
support for these interrupts. By specification, PCI interrupts are level-sensitive and
asserted/deasserted asynchronously to the PCI clock.
10.3.2.4
PCI Controller Clock and Reset Generation
The PCI Reset and PCI clock signals can be provided using general-purpose input/
output (GPIO) outputs or from an external source. The GPIO block is not part of the PCI
controller. See below for particular signals which may be used on various products for
these functions:
Both signals can be sourced from an external device as well. The Intel XScale processor
can generate the PCI reset and PCI clock outputs to satisfy the reset timing
requirements of the PCI bus.
A PCI startup sequence could be as follows:
1. Power-on reset occurs to the IXP45X/IXP46X network processors, the Intel XScale
processor starts execution (internal PLL assumed locked and internal clocks stable).
2. Software configures PCI reset and PCI clock GPIOs as outputs driving 0. A pull-
down on the GPIO pin chosen to drive the PCI reset signal is required. This pull-
down is required because the GPIO are at a tri-stated value until the device comes
completely out of reset and the PCI reset needs to be low from the start.
3. Wait 1ms to satisfy minimum reset assertion time of the PCI specification.
4. Configure the PCI clock GPIO for the proper PCI bus frequency (defined in the
section GPIO).
5. Enable the PCI clock GPIO to drive the PCI clock
6. Wait 100 µs to satisfy the “minimum reset assertion time from clock stable”
requirement of the PCI specification.
7. Set the PCI reset GPIO output to drive a 1. This releases the PCI bus.
Note:
The PCI reset can be asserted and de-asserted asynchronously with respect to the PCI
clock. It is also important to note the PCI reset signal cannot be the same signal as the
RESET_IN_N signal going to the processor due to PCI reset timing and PCI initialization
requirements.
10.3.2.5
PCI Configuration Register Access
As a PCI host performing configuration of the bus, the Intel XScale processor must
have read/write access to all of the PCI Configuration registers in the PCI Controller.
This access is provided via a set of three CSRs accessible from the AHB bus as
“AHB Accesses of Local PCI Configuration Registers” on page 534
10.3.2.5.1
PCI Configuration
Configuration of the PCI bus is performed by a PCI agent using configuration read and
write cycles. All devices on the bus have their configuration space read by the agent to
determine the attributes of the device. The agent then writes the appropriate
configuration registers in each device to, for example, set up the PCI memory map, and
Table 197.
PCI CLOCK and RESET Sourcing
Function
Intel
®
IXP42X
IXP45X/IXP46X network
processors
Clock Source
GPIO14
GPIO14
Reset Source
GPIO[13:0]
GPIO[13:0]