AN-206 Datasheet, PDF (1/8 Pages) Exar Corporation – EEPROM PROGRAMMING FOR PCIe UARTs

APPLICATION NOTE
AN206
EEPROM PROGRAMMING FOR PCIe UARTs
1.0 INTRODUCTION
Exar’s PCIe family of UARTs provides an interface to an Electrically Erasable Programmable Read Only Mem-
ory (EEPROM). The EEPROM is for storing information such as PCI vendor ID, PCI device ID and Class Code
etc. This application note describes how to correctly program the EEPROM for the Exar PCIe family of UARTs.
2.0 HARDWARE INTERFACE
The EEPROM interface consists of 4 signals, EEDI, EEDO, EECS, and EECK. This EEPROM is used to store
words of information such as Vendor ID, Device ID, Class Code, etc. This information is only used with the
plug-and-play auto configuration of the PCI local bus. The EEPROM is not needed when auto configuration is
not required in the application. However, if your design requires non-volatile memory for other purpose, it is
possible to store and retrieve data on the EEPROM through a special PCI device configuration register.
The Exar PCIe UART works with a 93C46-like EEPROM whose memory is configured as 16-bit words. The
93C46 is a 1K-bit memory device that can be configured as 64 x 16 (sixty four 16-bit words) or 128 x 8 (128
bytes). In order to work with Exar PCIe UARTs, it needs to be configured as 64 x 16. The Figure 1 below shows
the reference connections.
FIGURE 1. PCIE UART EEPROM INTERFACE
358/354/352
PCIe UART
EECS
EECK
EEDI
EEDO
VCC
4.7K
J1
8
VCC
1 _CS
ORG ⁶
2 _{SK EEPROM}
3 _DI 93C46
4 _DO
NU ⁷
GND
5
NOTE: The 4.7K pull-up resistor is required to load values from the EEPROM at power-up.
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