Echelon I/O Model Reference for Smart Transceivers and Neuron Chips - Manual (Page 173)

I/O Model Reference 163
Programming Considerations
The frequency of the square wave output is controlled by the clock-expr setting
and by the unsigned long output-frequency value passed to the io_out( ) function.
The pattern of this modulation frequency is controlled by an array of unsigned
long timing values, also passed to the io_out( ) function:
• The first value in this array controls the length of the first burst of
modulation frequency signal output—the output is active for this period.
• The second value in this array controls the length of an absence of the
modulation frequency signal—the output is idle for this period.
This pattern is then repeated by subsequent values in the array to produce a
sequence of frequency output bursts separated by idle periods. This array is
similar to the array generated by the edgelog input model.
The values in the timing-table array control the on and off time of the modulation
frequency output. This timing also is a product of the Neuron input clock, and is:
On/off period (μs) = (25.2 * value + 29.4) * S
In the formula above, the scaling factor S is determined by the input clock, as
shown in Table 60.
Table 60. Determining S
S
Input Clock Rate
(Series 3100) System Clock Rate
(Series 5000)
0.063 — 80 MHz
0.125 — 40 MHz
0.25 40 MHz 20 MHz
0.5 20 MHz 10 MHz
1 10 MHz 5 MHz
1.5259 6.5536 MHz —
2 5 MHz —
4 2.5 MHz —
8 1.25 MHz —
16 625 kHz —
The square wave output state is always toggled, between idle (off) and active (on),
at the end of the io_out( ) function. Typically, the number of elements in the
timing-table should always be an odd number, which will result in the output
being toggled to idle (turned off) at the end of the io_out( ) function. The last