Spartan 3E设备的配置失败

大家好，
我在我的董事会上看到一个非常有趣的问题。
我的设计使用XC3S200-4VQG100C。
需要在FPGA上工作的代码已经过测试，并且在评估板上正常运行。
我有一个专用电路板，其上安装了这个FPGA和其他模拟和数字组件。
该板具有电源，模拟和数字接地。
电源和模拟/数字地之间有5欧姆电阻。
模拟和数字接地短路。
以下是问题：
- 当我将正常代码烧入FPGA时，我可以看到我的数字和模拟地被拉高0.45V。
这是因为这两个地面之间存在电流。
这种下降使得ADC无法正常工作，因为参考输出从3V变为2.54V;
- 我将5欧姆值减小到1欧姆，ADC开始工作，但FPGA停止配置。
我检查了VCCO，VCC_AUX，VCCINT，一切都很好。
但FPGA没有配置;
- 我写了一个简单的代码来生成方波脉冲并测试电路板，我可以看到FGPA配置为2.5欧姆电阻（电源和模拟/数字地之间）但不是0欧姆或1欧姆;
- 如果我对PROM进行编程，它会被编程而没有任何问题;
- 我仍然不确定FPGA未配置的原因是什么。
请帮忙！
Swarup



以下为原文

Hi all,

I am seeing a very interesting issue on my board. I have a design using XC3S200-4VQG100C. The code that needs to work on the FPGA has been tested and is functional on the evaluation board. I have a proprietary board on which this FPGA has been mounted with other Analog and Digital components. The board has Power, Analog and Digital ground. The power and analog/digital ground have 5 ohm resistor between them. The analog and digital grounds are shorted. Below is the issue:

- When I have my normal code burnt into the FPGA, I can see my Digital and Analog Ground being pulled up by 0.45V. This is because there is current flow between these 2 grounds. This drop makes the ADC non-functional as the output of the reference changes from 3V to 2.54V;
- I reduced the 5 ohm value to 1 ohms and the ADC started working but the FPGA stopped configuring. I checked VCCO, VCC_AUX, VCCINT and all were perfectly fine. But the FPGA did not configure;
- I wrote a simple code to generate a square pulse and tested the board, I could see the FGPA getting configured for 2.5 ohm resistor (between Power and Analog/Digital ground) but not for 0 ohm or 1 ohm;
- If I program the PROM it gets programmed without any issues;
- I am still not sure what could be the reason for FPGA not getting configured.

Please Help!

Swarup