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Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
February 2007 HDD
Document Number: 305261; Revision: 004 47
General Hardware Design Considerations—Intel
®
IXP45X and Intel
®
IXP46X Product Line of
Network Processors
3.11.1 Signal Interface
3.11.2 Device Connection
There are a number of devices available that can interface to SSP or SPI ports, these
can range from RTC (Real-Time Clock), LCD (Liquid Crystal Displays), Digital Thermal
Sensor to Flash memory devices.
One of the most common usage for SSP or SPI port, is serial flash code storage. Serial
flash devices can be used to store board revision, serial numbers, or assembly
information. Figure 15 provides an example of a Serial Flash device interface to the
SSP port in the IXP45X/IXP46X network processors. For an additional example of SPI
interface, refer to Figure 14, in which a SLIC is connected to the SSP and HSS ports.
Table 19. Synchronous Serial Peripheral Port Interface
Name
Input/
Output
Pull
Up/
Down
Recommendations
SSP_SCLK O No Serial bit clock.
SSP_SFRM O No Serial frame indicator.
SSP_TXD O No Transmit data (serial data out).
SSP_RXD I Yes
Receive data (serial data in).
Should be pulled high through a 10-KΩ resistor when not being utilized in the system.
SSP_EXTCLK I Yes
External clock input.
Should be pulled high through a 10-KΩ resistor when not being utilized in the system.
Figure 15. Serial Flash and SSP Port (SPI) Interface Example
SPI Flash
Intel
®
IXP46X
Product Line
Network Processors
SSP Interface
SSP_TXD
SSP_SFRM
SSP_EXTCLK
SSP_SCLK
SSP_RXD
External Oscillator
D I
CS_N
CLK
DO
7.2 KHz
to 3.6864 MHz
B4109-001