[问答]

怎么从DCM和引脚强度输出时钟

问答对人有帮助，内容完整，我也想知道答案 0 你好。对不起，如果这个问题很愚蠢，但我的学习背景是物理学，我正在学习当前工作中的一些电子学^ _ ^ 我正在使用带有Spartan-3 FPGA的电路板。在电路板上，有一个24 MHz的clk可用。我将这个时钟放在FPGA引脚上，然后使用单个DCM，我可以产生一个40 MHz的时钟。然后，我将这个时钟从FPGA发送到我必须测试的ASIC芯片。问题是输出clk（clk_40）看起来像一个正弦波，而我需要一个（尽可能多）精确的方波。据一些同事说，问题似乎是“输出引脚不够强大，无法驱动外部逻辑”。现在，对我而言，这句话在真正意义上有点模糊，但是......有可能改变这个“力量”的针吗？目前，在项目的UCF中，我将clk引脚设置为IOSTANDARD = LVCMOS12。这是我必须改变的吗？抱歉愚蠢的问题^ _ ^ 弗朗西斯。以上来自于谷歌翻译以下为原文 Hi. Sorry if the question is stupid, but my study background is in physics and I'm learning a bit of electronics for my current work ^_^ I'm using a board with a Spartan-3 FPGA. On the board, there is a 24 MHz clk available. I put this clock on an FPGA pin and then using a single DCM I can generate a 40 MHz clock. Then, I send this clock out of the FPGA to a ASIC chip I have to test. The problem is that the output clk (clk_40) looks like a sin wave, instead I need a (as most as possible) precise square wave. According to some colleagues, it seems that the problem is that the "output pin is not strong enough to drive the outside logic". Now, to me this sentence is a bit obscure in the real meaning, but..is it possible to change this "strength" of the pin? At the moment, in the UCF of the project I set the clk pin as IOSTANDARD = LVCMOS12. Is this that I have to change? Sorry for the stupid question ^_^ Francesco. 0
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答案对人有帮助，有参考价值 0 弗朗西斯在您对信号质量过于沮丧之前，您可能需要确保自己正在使用适当的测量工具。示波器的输入带宽是多少？如果它不是你测量频率的至少5倍，那么波形就不会真实代表你正在看的信号。还要确保你有良好的接地连接，在进行信号完整性测量时，最好使用短接地引线。经常示波器探头配有猫须式接地探头，可直接安装在地面上在探头尖端环。这将是理想的探测器。否则，看看信号强度在你的“正弦波”上。如果问题确实与引脚驱动强度有关，你应该期望一个较低的幅度和一个正弦波形状。 HTH，的Gabor - Gabor 以上来自于谷歌翻译以下为原文 Francesco, Before you get too discouraged about the signal quality, you may want to make sure you are using the proper measurement tools. What it the input bandwidth of the oscilloscope? If it's not at least 5 times the frequency you're measuring, the wave shape will not really represent the signal you're looking at. Also make sure you have a good ground connection, preferably using a short grounding lead when making signal integrity measurements. Often scope probes come with a cat-whisker style ground probe that mounts directly to the ground ring at the tip of the probe. This would be the ideal probe to use. Otherwise, look at the signal strength on your "sine wave." If the problem is really with the pin drive strength, you should expect a lower amplitude as well as a sinusoidal wave shape. HTH, Gabor -- Gabor

2019-5-22 15:19:56 评论举报杨玲