Echelon I/O Model Reference for Smart Transceivers and Neuron Chips - Manual (Page 135)

I/O Model Reference 125
Important: The first measured value of a timer/counter is always discarded to
eliminate the possibility of a bad measurement after the chip comes out of a reset
condition.
Single events cannot be measured with the timer/counters . Figure 47 shows an
example of how the timer/counter objects are processed with a Neuron C when
statement.
TIME
INPUT
SIGNAL
STOP TIMER/COUNTER
SET FLAG LOAD NEW VALUE
INTO REGISTER
START
TIMER/
COUNTER
READ TIMER/COUNTER FLAG AND
REGISTER FROM THE PREVIOUS EVENT
END OF
io_in()
START OF
io_in()
STOP
TIMER/COUNTER
SET FLAG
LOAD EVENT
REGISTER
START
TIMER/
COUNTER
TIME
INPUT
SIGNAL
(event)
READ
TIMER/
COUNTER
FLAG AND
REGISTER
CLEAR FLAG
END OF
io_in()
START OF
io_in()
statement)
t
fin
t
ret
t
fin
t
ret
Example of a
when
statement
evaluating to true
(unless it is the
first event)
Example of a
when
statement
missing a current
event but
evaluating a
previous event
when (
Figure 47. Example of when Statement Processing for the Ontime Input Object
As with all CMOS devices, floating I/O pins can cause excessive current
consumption. To avoid this excess current consumption, declare all unused I/O
pins as bit output. Alternatively, unused I/O pins can be connected to + VDD5
(for Series 3100 devices), +VDD33 (for Series 5000 devices), or GND.
Dualslope Input
The dualslope I/O model is used to control and measure the integration periods of
a dualslope integrating analog-to-digital (A/D) converter. You can use this I/O
model to implement low-cost A/D converters for analog input.
The I/O model controls a timer/counter output pin based on a control_value
argument and the state of a timer/counter input pin. When combined with
external analog circuitry, the Neuron Chip or Smart Transceiver performs A/D
measurements with 16 bits of resolution for as little as a 3.278 ms integration
period for a Series 3100 device with a 40 MHz input clock (the period scales with