Specifications

Chapter 3 – Input/Output Interfaces

74 PL 3120/PL 3150/PL 3170 Power Line Smart Transceiver Data Boo

The leveldetect input object can be used for detection of asynchronous attachments of 1-Wire Memory devices to the PL

Smart Transceiver. In such a case, the leveldetect input object is overlaid on top of the Touch I/O object. Refer to the

Neuron C Programmer’s Guide for information on I/O object overlays.

For more specific information on the mechanical, electrical, and protocol specifications, refer to the 1-Wire device

information available from Dallas Semiconductor Corporation.

Wiegand Input

This input object provides an easy interface to any card reader supporting the Wiegand standard. Data from the reader is

presented to the PL Smart Transceiver through the use of two of its first eight I/O pins, IO0 – IO7. Up to four Wiegand

devices can be connected to the PL Smart Transceiver. Data is read MSB first.

Wiegand data starts as a negative-going pulse on one of the two pins selected. One input represents a logical 0 bit and

the other pin a logical 1, as selected through the I/O declaration. The bit data on the two lines are mutually exclusive and

are spaced at least 150µs apart. Figure 3.34 shows the timing relationship of the two data lines with respect to each

other and the PL Smart Transceiver.

Any unused I/O pin from IO0 to IO7 can be optionally selected as the timeout pin. When the timeout pin goes high, the

function aborts and returns. The application processor’s watchdog timer is automatically updated during the operation of

this input object.

Incoming data on any of the Wiegand input pins is sampled by the PL Smart Transceiver every 200ns at a 10MHz clock

(scales inversely with the clock frequency). because the Wiegand data is usually asynchronous, care must be taken in the

application program to ensure that this function is called in a timely manner in order that no incoming data is lost.