I/O上拉电阻器的问题

我在使用xilinx芯片的许多电路板上遇到了一些奇怪的问题。
在我们的3个I / O引脚上，我连接了施密特逆变器，驱动了一些LED。
这一直有效，如果没有加载xilinx程序，这些LED将保持开启状态（逆变器从xilinx输出的逻辑电平为0，输出逻辑电平为1，从而导通LED）。
现在我已经得到了3个LED中的2个不会出现的电路板，直到xilinx芯片被编程，初始化，然后告诉LED指示灯亮起。
我正在使用的I / O引脚如下：
44  -  IO / VREF_5
46  -  IO_L28P_5
47  -  IO_L28N_5
我在VCC上的配置是3.3V，VCCAUX是2.5V，而我的HSWAP_EN是2.5V。
我正在使用带有TQ144封装的XC3S200。
据我所知，HSWAP_EN上的2.5V构成1逻辑电平，应禁用上拉电阻，使LED亮。
无论出于何种原因，引脚44和47似乎都激活了上拉电阻，而引脚46使它们无效。
而且我说“似乎”因为我无法知道因为我无法测量是否有上拉电阻（据我所知）。
但是，因为当我使用标准dmm探测该引脚时，LED导通，表明该问题与xilinx中的上拉电阻有关。
有时，当我探测引脚44时，LED保持开启状态，直到我在xilinx（或与物理板上的xilinx相当远的施密特反相器）上吹气，这使LED关闭（奇怪）。
任何人都知道会发生什么事吗？
我发现更换一些这些电路板上的EEPROM解决了这个问题，但我仍然有一大批电路板，其中更换EEPROM没有任何影响。
我不相信这是Xilinx引起的问题，我已经尝试在其中一块没有解决问题的电路板上更换芯片。



以下为原文

I am having some weird issues with a number of boards using the xilinx chip. On 3 of our I/O pins I have a schmitt inverter hooked up which drives some LEDs. This has always worked so that if the xilinx program isn't loaded these LEDs would stay on (inverter gets a logic level of 0 from the xilinx outputting a logic level of 1 therefore turning on the leds). Now I've been getting boards where 2 of the 3 leds dont come on until the xilinx chip is programmed, initialized, and then tells the leds to come on.

The I/O pins I am using are the following:

44 - IO/VREF_5
46 - IO_L28P_5
47 - IO_L28N_5

My configuration on VCC is 3.3V, VCCAUX is 2.5V and my HSWAP_EN is 2.5V. I am using the XC3S200 with the TQ144 footprint.

As I understand 2.5V on HSWAP_EN constitutes a 1 logic level which should disable the pull up resitiors allowing the LEDs to come on. For whatever reason pin 44 and 47 seem to have the pull up resistors activated while pin 46 has them deactivated. And I say "seem" because I have no way to know as I can't measure if the pull up resistor is there (as far as I know). However, since when I probe that pin usin a standard dmm the led turns on suggesting the issue is related to the pull up resistors in the xilinx. Sometimes when I probe pin 44 the LED stays on like its supposed to until I blow on the xilinx (or on the schmitt inverter which is fairly far away from the xilinx on the physical board) which turns the LED off (weird).

Anyone have any idea what could be going on? I found replacing the EEPROM on some of these boards fixed the issue, but I still have a large batch of boards where replacing the EEPROM had no effect. I dont believe this is the Xilinx causing the problem, I have tried replacing this chip on one of the boards which didn't solve the issue.