Specifications

Chapter 3 – Input/Output Interfaces
70 PL 3120/PL 3150/PL 3170 Power Line Smart Transceiver Data Boo
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4. Test the input clock for a low input level. This is the test for the falling edge of the input clock. If the input clock is
still high, sample the timeout event pin and abort if high.
5. When the input clock is low, return to step 1 if there are more bits to be processed.
6. Else return the number of bits processed.
When either clock input test fails (that is, the clock is sampled before the next transition), there is an additional
timeout check time of 19.8µs (wait for clock high) or 19.2µs (wait for clock low) added to that stage of the
algorithm.
The chip select logic for the Neurowire slave can be handled by the user through a separate bit input object, along with
an appropriate handshaking algorithm implemented by the user application program. In order to prevent unnecessary
timeouts, the setup and hold times of the chip select line, relative to the start and end of the external clock, must be
satisfied.
The timeout input pin can either be connected to an external timer or to an output pin of the PL Smart Transceiver that is
declared as a oneshot object.
Serial Input/Output
The Serial I/O object is still provided for legacy support. Echelon recommends using the SCI (UART) instead of the
legacy software I/O object (See SCI (UART) Input/Output section). The hardware UART provides much higher
performance with lower software overhead.
Pin IO8 can be configured as an asynchronous serial input line, and pin IO10 can be configured as an asynchronous
serial output line. The bit rates for input and for output can be independently specified to be 600, 1200, 2400, or 4800
bits/second at a 10MHz input clock rate. The data rate scales proportionally to the input clock rate.
The frame format is fixed at 1 start bit, 8 data bits, and 1 stop bit; and up to 255 bytes can be transferred at a time. Either
a serial input or a serial output operation (but not both) can be in effect at any one time. The interface is half-duplex
only. This function suspends application processing until the operation is completed. On input, the io_in() request
will time out after 20 character times if no start bit is received. If the stop bit has the wrong polarity (it should be
a 1), the input operation is terminated with an error. The application code can use bit I/O pins for flow control
handshaking if required. This function is useful for legacy applications that transfer data to serial devices such as
terminals, modems, and computer serial interfaces (see Figures 3.31 and 3.32).