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maximum frequency for encoder input of PMAC2 PC/104


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It depends on your SCLK frequency which can be adjusted by I903 parameter. Here is a quote from users manual:

 

The SCLK frequency must be at least four times higher than the maximum encoder cycle (line) frequency input, regardless of the quadrature decoding method used (with the most common times-4 decode, the SCLK frequency must be at least as high as the count rate). In actual use, due to imperfections in the input signals, a 20 – 25% safety margin should be used.

The default SCLK frequency of 9.83 MHz is acceptable for virtually all applications. It can accept encoder signal cycle frequencies of up to about 2 MHz (8 MHz count rates) – with safety margin – and still provide decent digital filtering. This frequency may be changed by factors of two, up to 19.66 or 39.32 MHz on most designs, or down to as low as 1.25 MHz or 306 kHz on most designs. On some designs, an external SCLK signal can be provided. If very high encoder count rates are required, the SCLK frequency may have to be raised; if better filtering is required to prevent count errors, the SCLK frequency may have to be lowered.

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