Specifications

Chapter 3 – Input/Output Interfaces
90 PL 3120/PL 3150/PL 3170 Power Line Smart Transceiver Data Boo
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The internal counter increments with every occurrence of an active input edge. Every 0.839 second, the content of the
counter is saved and the counter is then reset to 0. This sequence is repeated indefinitely.
The actual active edge of the input depends on whether or not the invert option was used in the declaration of the
function block. The default is the negative edge.
Quadrature Input
A timer/counter can be configured to count transitions of a binary Gray code input on two adjacent input pins. The Gray
code is generated by devices such as shaft encoders and optical position sensors which generate the bit pattern
(00,01,11,10,00, …) for one direction of motion and the bit pattern (00,10,11,01,00, …) for the opposite direction.
Reading the value of a quadrature object gives the arithmetic net sum of the number of transitions because the last time
it was read (-16,384 to 16,383). The maximum frequency of the input is one-quarter of the input clock rate, for example
2.5MHz with a 10MHz PL Smart Transceiver input clock. Quadrature devices can be connected to timer/counter 1 via
pins IO6 and IO7, and timer/counter 2 via pins IO4 and IO5 (see Figure 3.47). If the second input transitions low while
the first input is low and high while the first input is high, the counter counts up. Otherwise, the count is down.