Motorola DSP56301 - Manual (Page 29)

Peripherals
Overview 1 -13
1.7.4 Serial Communications Interface (SCI)
The SCI provides a full-duplex port for serial communications with other DSPs,
microprocessors, or peripherals such as modems. The SCI interfaces without additional logic
to peripherals that use TTL-level signals. With a small amount of additional logic, the SCI can
connect to peripheral interfaces that have non-TTL level signals, such as the RS-232C,
RS-422, and so forth. This interface uses three dedicated signals: transmit data, receive data,
and SCI serial clock. It supports industry-standard asynchronous bit rates and protocols, as
well as high-speed synchronous data transmission (up to 12.5 Mbps for a 100 MHz clock).
SCI asynchronous protocols include a multidrop mode for master/slave operation with
wakeup on idle line and wakeup on address bit capability. This mode allows the DSP56301 to
share a single serial line efficiently with other peripherals.
Separate SCI transmit and receive sections can operate asynchronously with respect to each
other. A programmable baud-rate generator provides the transmit and receive clocks. An
enable vector and an interrupt vector allow the baud-rate generator to function as a
general-purpose timer when the SCI is not using it or when the interrupt timing is the same as
that used by the SCI.
1.7.5 Triple Timer Module
The triple timer module is composed of a common 21-bit prescaler and three independent and
identical general-purpose 24-bit timer/event counters, each with its own memory-mapped
register set. Each timer has the following properties:
n A single signal that can function as a GPIO signal or as a timer signal
n Uses internal or external clocking and can interrupt the DSP after a specified number
of events (clocks) or signal an external device after counting internal events
n Connects to the external world through one bidirectional signal. When this signal is
configured as an input, the timer functions as an external event counter or measures the
external pulse width/signal period. When the signal is used as an output, the timer
functions as either a timer, a watchdog, or a pulse width modulator.