Receive Data (Rxd); Transmit Data (Txd); Sci Serial Clock (Sclk) - Motorola DSP56303 User Manual

I/O Signals
To enable SCI interrupts, program the SCI control registers before any of the SCI signals are
programmed as SCI functions. In this case, only one transmit interrupt can be generated
because the Transmit Data Register is empty. The timer and timer interrupt operate regardless
of how the SCI pins are configured, either as SCI or GPIO.
8.2.1

Receive Data (RXD)

This input signal receives byte-oriented serial data and transfers the data to the SCI receive
shift register. Asynchronous input data is sampled on the positive edge of the receive clock (1
) if the SCI Clock Polarity (SCKP) bit is cleared.
SCLK
signal ( ) when the SCI
PE0
8.2.2

Transmit Data (TXD)

This output signal transmits serial data from the SCI transmit shift register. Data changes on
the negative edge of the asynchronous transmit clock (
is stable on the positive edge of the transmit clock.
( ) when the SCI
PE1 TXD
8.2.3

SCI Serial Clock (SCLK)

This bidirectional signal provides an input or output clock from which the transmit and/or
receive baud rate is derived in Asynchronous mode and from which data is transferred in
Synchronous mode.
SCLK
function is not in use. This signal can be programmed as
on , since the clock does not need to be transmitted in Asynchronous mode. Because
TXD
is independent of SCI data I/O, there is no connection between programming the
and data coming out the
SCLK
8-4
function is not in use.
RXD
function is not in use.
can be programmed as a GPIO signal (
signal.
TXD
DSP56303 User's Manual
can be configured as a GPIO
RXD
) if SCKP is cleared. This output
SCLK
can be programmed as a GPIO signal
TXD
) when the SCI
PE2
when data is being transmitted
PE2
SCLK
SCLK
signal as
PE2