BitFlow Cyton-CXP, Hardware Reference Manual

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Encoder Divider Details The Cyton-CXP
CYT-6-2 BitFlow, Inc. Version A.0
6.2 Encoder Divider Details
6.2.1 Formula
The following formula shows the equation used to scale the encoming encoder rate
into the camera’s line rate:
Where:
Fout = The frequency used to driver the camera or the NTG or the CTabs
Fin = The encoder (input) frequency
N = An integer between 0 and 6 (set by the register ENC_DIV_N)
M = An integer between 1 and 1023 (set by the register ENC_DIV_M)
The above formula provides an effective scaling factor from 0.001 (N = 0, M =1023) to
64 (N = 6, M = 1). Not every scaling factor can be acheived between these two
extremes, and the scaling factors are not evenly distributed. However, a scaling factor
can be generally found that meets the requirments of most applications.
6.2.2 Example
Let’s assume that the encoder frequency (Fin) is 10 KHz and that we need an output
(Fout) of ~30 KHz. This means that we need to multiply by 3. Set N = 6 and M = 21.
This will a scaling factor of 3.048. The result is an effective line rate of 30.48 KHz.
6.2.3 Restrictions
Because the encoder divider uses a digital PLL run by a 50 MHz clock, not all encoder
input frequencies can be accurately scaled. The PLL has been designed to work in
most machine visions applications. Support, therefore, is provided for the following
inpute frequency range:
Minimum input encoder frequency: 1.6 KHz
Maximum input encoder frequency: 300 KHz
F
out
F
in
2
N
M
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