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Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors—Expansion Bus
Controller
Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
Developer’s Manual
August 2006
708
Order Number: 306262-004US
The chip-level memory map used is determined by the state of bit 31. At system reset
this bit is a ‘1’ and the memory map places the Expansion Bus at address 0x00000000
through 0x0FFFFFFF. This allows boot code stored in flash to be retrieved and executed
as required.
Once the boot sequence completes this bit is written to a ‘0’, switching the default
system memory map to place the DDRI SDRAM controller at address 0x00000000 to
0x0FFFFFFF. The Expansion bus controller now resides at address 0x50000000 to
0x5FFFFFFF. Weak pull-up resistors are placed on each expansion bus address pin.
8
USB Clock
EX_ADDR[8]
Controls the USB clock select
1 = USB Host/Device clock is generated internally
0 = USB Device clock is generated from GPIO[0]. USB Host clock is
generated from GPIO[1]. When generating a spread spectrum
clock on OSC_IN, GPIO[0] can be driven from the system board to
generate a 48 MHz clock for the USB Device and GPIO[1] can be
driven from the system board to generate a 60 MHz clock for the
USB Host.
7
32_FLASH
EX_ADDR[7]
Refer to the table found in 8/16_FLASH bit (bit 0) of this register.
6
EXP_ARB
EX_ADDR[6]
Configures the Expansion bus arbiter
0 = External arbiter for Expansion bus.
1 = Expansion bus controller arbiter enabled
5
EXP_DRIVE
EX_ADDR[5]
Expansion bus low/medium/high drive strength. The drive strength
depends on EXP_DRIVE and EXP_MEM_DRIVE configuration bits.
EXP_MEM_DRIVE EXP_DRIVE Expansion drive strength
--------------------------------------------------------------------------
-------------
0 0 Reserved
0 1 Medium Drive
1 0 Low Drive
1 1 High Drive
4
PCI_CLK
EX_ADDR[4]
Sets the clock speed of the PCI Interface
0 = 33 MHz
1 = 66 MHz
3
(Reserved)
EX_ADDR[3]
(Reserved). EX_ADDR[3] must not be pulled down during address
strapping. This bit must be written to ‘1’ if performing a write to
this register.
2
PCI_ARB
EX_ADDR[2]
Enables the PCI Controller Arbiter
0 = PCI arbiter disabled
1 = PCI arbiter enabled
1
PCI_HOST
EX_ADDR[1]
Configures the PCI Controller as PCI Bus Host
0 = PCI as non-host
1 = PCI as host
0
8/16_FLASH
EX_ADDR[0]
Specifies the data bus width of the FLASH memory device found on
Chip Select 0. The data bus is based upon bits 0 and 7 of
Configuration Register 0.
32_FLASH 8/16_FLASH Data bus size
---------------------------------------------------------------
0 0 16-bit
0 1 8-bit
1 0 Reserved
1 1 32-bit
Table 229.
Configuration Register 0 Description (Sheet 2 of 2)
Bit
Name
Reset Value
Description