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ID: 974
实例类型: faq
分类: Device Programming
相关: Diamond Programmer
产品系列: All FPGA

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Can the ispVM tool control the TCK duty cycle and/or frequency?

The actual TCK frequency depends on a number of factors including PC speed, parallel port vs. USB cable, USB 1.1 vs. 2.0.

Under ispVM Project -> Project Settings, Advanced, you can use the TCK Low Pulse Width Delay option to slow down the TCK.


Currently, this option delays the low pulse width as follows:



  • Setting TCK Low Pulse Width Delay to 2 will stretch the low pulse approximately twofold.
  • Setting it to 3 will stretch the low pulse approximately threefold.

However, the setting is not exact. The exact ratio, like the frequency, will vary from system to system. It is simply a tool a user can use to debug programming issues due to noise. It is not meant to provide exact frequency or duty cycle control. 

You cannot stretch the high pulse of the TCK on the parallel port because some PCs will create a glitch doing so and the device will see a double clock edge.


Separate duty cycle control is not available.

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