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I/O Model Reference 131

Table 50. Edgelog Input Latency Values for Series 3100 Devices

Symbol Description Minimum Typical Maximum

setup

Input data setup 0 — —

win

Input pulse width 1

T/C clk

— 65534

T/C

clks

hold

io_in() call to data input edge for inclusion of

that pulse

26.4 μs — —

wtcp

Two consecutive pulse widths 104 μs — —

oret

Return on overflow — 42.6 μs —

ret

Return on count termination — 49.6 μs —

Note:

T/C clk

represents the period of the clock used during the declaration of the I/O object.

Programming Considerations

For edgelog input, the io_in( ) function requires a pointer to a data buffer, into

which the series of unsigned long values are stored, and a count argument, which

controls the number of values to be stored. The values stored represent the units

of clock period between input signal edges, rising or falling. The io_in( ) function

returns an unsigned short int that contains the actual number of edge-to-edge

periods stored. No input events are associated with an edgelog input object.

During the io_in( ) function call, the measurement process stops whenever the

maximum period is exceeded. In this case, the value returned will not be equal to

the count argument passed.

If a preload value is specified, it must be added to the value returned by io_in( ).

The resulting addition may cause an overflow, but this is normal.

This I/O model uses both of the Neuron timer/counters.

Neuron C Resources

The following functions are provided specifically for use with the edgelog I/O

object:

•

io_edgelog_preload( )

Changes the maximum value for each period measurement. The maximum

value may range from 1 to 65535; the default value is 65535. This function is

only used for an edgelog device that is

not

declared with the single_tc option

keyword.

•

io_edgelog_single_preload( )

1 2 ... 136 137 138 139 140 141 142 143 144 145 146 ... 208 209

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