我在”pcb设计“上看到的别人提出的问题
自己也有相同疑问
请指教

小弟最近用xc2v2000做了一个板子，基本上工作正常，但是加上程序后（一个数字信号处理的程序，占用了130万门的资源，输入时钟40MHz，内部倍频到80Mhz）功耗特别大，大概有4～5W的样子。这个时候发现板子工作不太稳定，常常工作一段时间就停了下来（表现在电流减小），拍拍板子又开始工作了，但是下载一个比较小的程序就不会出现这个问题，请大家帮我分析一下吧
下面提出的三个问题可能和程序工作不稳定这一现象有关，请分析：
关于fpga板，有几个问题我尚未弄清楚：
1.看资料的时候，知道DXN和DXP是接温敏二极管的，但是温敏二极管有什么作用呢？我没有找到详细说明，请大侠指教。我画那块板子的时候，这两个专用引脚是悬空的，会不会有什么问题？
2.资料上说VBATT是接电池，用来在调电的情况下保存下载到fpga中的程序，当不用电池时，vbatt引脚应该悬空，但是我把vbatt、vcco和vccaux统统接到3.3V上，会有问题嘛？
小弟最近就要画新版了，急需弄清楚这个问题，请大家不吝赐教
关于设计方面，我尚有一个疑问：
有人说，把lut配置成16bit移位寄存器（srl16）需要在设计中使用startup，但是viterx2系列中好像没有这个东西呀，是否必须？如何使用？

问题一
You can access the Virtex temperature-sensing diode through the DXP (Anode) and DXN (Cathode) pins. The DXP and DXN pins are connected to a diode-connected transistor, which creates a remote sensor. (These additional pins are not available on all packages.)
The DXP and DXN pins are dedicated pins and cannot be accessed through the software tools. These pins are attached to the substrate/die itself. They are always available, and you do not need to perform anything special in your design to use them. If the temperature-sensing feature is not used, then the DXP and DXN pins can be left unconnected.
The temperature-sensing diode is one part of a two-part system that incorporates a Temperature Sensor Interface Chip. To complete the system, you need a temperature sensor device, which connects to the Virtex device by means of the DXP and DXN pins. On most temperature sensing devices, corresponding pins connect to DXP and DXN. You can then set the upper and lower limits, and the temperature sensor creates an interrupt when these bounds are exceeded. (The interrupt is simply an output pin on the sensor.) You can then use this output to turn "off" the clock or turn "on" a fan to reduce heat.
The accuracy of the temperature measurement does not depend on the diode (DXN/DXP pins), since the voltage vs. temperature curve is the physical nature of the diode. The accuracy relies upon the temperature sensor device, which translates the IV vs. temperature curves into a temperature reading. The data sheet of the temperature sensors listed below contains the accuracy specifications.
Examples of Temperature Sensors
1. The Maxim 1617 Remote/Local Temperature Sensor with SMBus Serial Interface. For more information on this device, refer to:
http://www.maxim-ic.com
(For the data sheets, see:
http://pdfserv.maxim-ic.com/ds/en/MAX1617.pdf).
2. The LM83 Triple-Diode Input and Local Digital Temperature Sensor with Two-Wire Interface from National Semiconductor.
For more information regarding on this device, refer to:
http://www.national.com
(For the data sheet, see:
http://www.national.com/ds/LM/LM83.pdf)
不用的话，悬空
问题二，按照DATASHEET上的说法，没问题
“把lut配置成16bit移位寄存器（srl16）需要在设计中使用startup”，我怎么不清楚？麻烦你提供详细的资料，我可以帮你解决。

非常感谢楼主解答