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130 Timer/Counter Input Models

For a Series 5000 device, this I/O model measures a series of both high and low

input signal periods on a single input pin, IO_4, in units of the clock period:

time_on/time_off (ns) = value_stored * 2000 * 2^(value) / 10 MHz

where value ranges from 0..15

Edgelog input can be used to capture complex waveforms such as infrared

command input (see also

Infrared Input

on page 134), or to decode any type of

bitstream that contains data in the time domain (an arbitrarily-spaced stream of

input edges or pulses), such as bar code input.

This model applies to Series 3100 Neuron Chips and Smart Transceivers, and to

Series 5000 Neuron Processors and Smart Transceivers.

Hardware Considerations

The measurement series starts on the first rising (positive) edge, unless the

invert keyword is used in the I/O object declaration. The measurement process

stops whenever an overflow condition is sensed on either timer/counter.

The resolution and range of the timer/counter period options is described in

Timer/Counter Resolution and Maximum Range

on page 188.

Timer/Counter 1

Timer/Counter 2

IO10

IO9

IO8

IO0

IO1

IO2

IO3

IO4

IO5

IO6

IO7

Input

Bit Stream

IO11

END

OF io_in()

OVERFLOW

TIME

INPUT

(IO4)

START OF

io_in()

win

wtcp

ret

oret

hold

setup

Figure 49. Edgelog Input and Timing

1 2 ... 135 136 137 138 139 140 141 142 143 144 145 ... 208 209

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