Components and Control
The Neon
NEO-3-2
BitFlow, Inc.
Version G.5
3.2 Components and Control
3.2.1 Periods and Frequencies
The NTG consists of a programmable signal generator based on a crystal controlled
clock. This clock is always running and is unrelated to the camera connected or how
other parts of the board are programmed. The base frequency of the clock is
designed to handle any line scan camera system. For area scan cameras the clock can
be divided 128 to increase the time range if very slow frame rates and/or line expo-
sures are needed. To use the divided clock, program the bit NTG_TIME_MODE to 1.
The frequency of the clock is different for the different frame grabber families as
shown in Table 3-1.
The are two main timing registers: NTG_RATE, which controls the line/frame rate
period, and NTG_EXPOSURE, which controls the exposure period. These are both 28
bits, which should be enough to support almost all applications. Table 3-2 shows the
resulting ranges
The NTG uses a counter internally to create the programmed waveforms. Because the
NTG registers can be set for very long times, reprogramming the NTG can be time
consuming. In order to speed up modifications to the NTG parameters, the register
NTG_RESET can be used. Poke this bit to a 1 resets the NTG counter to zero, and
starts a new cycle with the latest register values.
Note: Use the base frequency when a high resolution timer is needed (fine
granularity). Use the reduced frequency when long exposure periods and/or slow
frame rates are needed (course granularity) You can use which ever mode suits your
application regardless of whether you are using a line scan or an area scan camera..
Table 3-1 NTG Base Frequencies
Family
Base frequency
Reduced frequency
Karbon, Neon
7.3728 MHz
57.6000 KHz
Alta-AN
5 MHz
39.0625 KHz
Table 3-2 NTG Period Ranges
Family
Mode
Granularity (1 clock period)
Max Period
Karbon, Neon
Area
~17.4 microsecond
~77 minutes
Line
~136 nanoseconds
~36 seconds
Alta-AN
Area
25.6 microseconds
~114 minutes
Line
200 nanoseconds
~ 53 seconds
Содержание NEO-PCE-CLB
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