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参数资料
| 型号： | EEPROMFLASH |
| 英文描述： | Microcircuit, Linear, High Speed, Operational Amplifier, Monolithic Silicon; Temperature Range: -55°C to 125°C; Package: 8-Can |
| 中文描述： | 56F83xx借给混合应用EEPROM的能力FlashEE |
| 文件页数： | 2/4页 |
| 文件大小： | 79K |
| 代理商： | EEPROMFLASH |
How to Bypass Misprogrammed EEPROM that is Hanging Your System
2
Introduction
Most of the PCnet family Ethernet controllers support a serial configuration EEPROM. The EEPROM may be a DIP or a
surface mount device, but in either case, it's external to the PCnet controller. At power-on and hardware reset, the PCnet
controller automatically senses the presence of the EEPROM and reads the contents into internal configuration and control
registers.
When programmed correctly, the configuration EEPROM feature is great because your controller automatically initializes
itself on power-on and system reset.
If the EEPROM contents is accidentally misprogrammed, it's possible to see strange system behavior including a system
hang. This can occur because some of the internal control registers control activity on the bus interface. If you load these
registers with illogical values, you might cause the controller to grab the bus and prevent other bus activity.
When this occurs, you find that you need to restart the system so you can reprogram the EEPROM but you can't because the
system hangs with the offending PCnet adapter card plugged in.
Bypassing the EEPROM
There's a neat little trick you can perform to shut off the PCnet controller and regain control of the system so you can
reprogram the serial EEPROM. During the power-on or hardware reset, you simply need to force the controller to think it's
detected an EEPROM checksum error while reading the EEPROM. A checksum error will cause the controller to enter a
special sleep mode where it's quiescent on the bus.
When you run one of the EEPROM programming utilities (e.g. EESETUP or Aminstal), they know how to wake up the
controller and perform the EEPROM programming operation.
Magic Shorting Step
While the system is being powered on or a hardware reset is being applied, short pins 4 and 5 of the serial EEPROM. What
you're doing is shorting the EEPROM data out pin (DO) to ground causing the data to look like a bunch of zeros. The
bottom line is that the CRC check will fail and the controller will go off into it's quiescent state.
For AMD adapter card designs, the EEPROMs used are 93C57, 93C56, and 93C46. These EEPROMs are MICROWIRE
compatible, physically compatible with the pin shorting directions given, and are compatible with the EEPROM
programming software supplied by AMD.
___
CS | 1 |_| 8 | Vcc
SK | 2
7 | No Connect
DI | 3
6 | ORG (x16)
DO | 4
5 | GND
---------
Table 1. Serial EEPROM Pin Configuration
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