Specifications

PL 3120/PL 3150/ PL 3170 Power Line Smart Transceiver Data Book 83
Dualslope Input
This input object uses a timer/counter to control and measure the integration periods of a dualslope integrating analog to
digital converter (see Figure 3.41). The timer/counter provides the control output signal and senses a comparator output
signal. The control output signal controls an external analog multiplexer which switches between the unknown input
voltage and a voltage reference. The timer/counter’s input pin is driven by an external comparator which compares the
integrator’s output with a voltage reference. At the end of conversion, the external comparator will drive a low level to
one of pins IO4 – IO7. If external circuitry indicates “end of conversion” with a high level, use the invert keyword in
the I/O declaration.
The resolution and range of the timer/counter period options is shown in Table 3.8 in the Notes section of this chapter.
Timer/Counter 1
Timer/Counter 2
IO10
IO9
IO8
IO0
IO1
IO2
IO3
IO4
IO5
IO6
IO7
mux
Control Output
From
Comparator
IO11
OUTPUT
(IO0 OR IO1)
START OF
io_in_request()
END OF
io_in()
LATCHED COUNT
AVAILABLE TO
APPLICATION
START
OF io_in()
TIME
INPUT
(IO4 TO IO7)
ANALOG SWITCH
CONTROL
COMPARATOR
OUTPUT
INTEGRATOR
OUTPUT
V
thresh
t
reqo
t
fin
Symbol Description Min Typ Max
t
reqo
io_in_request() to output toggle
— 75.6 µs —
t
fin
Input function call and return — 82.8 µs —
Figure 3.41 Dualslope Input Object