Texas Instruments TMS320C3x - Manual (Page 394)

Serial Ports
12-15 Peripherals
12.2 Serial Ports
The ’C30 has two totally independent bidirectional serial ports. Both serial ports
are identical, and there is a complementary set of control registers in each one.
Only one serial port is available on the ’C31 and the ’C32. You can configure
each serial port to transfer 8, 16, 24, or 32 bits of data per word simultaneously
in both directions. The clock for each serial port can originate either internally,
through the serial port timer and period registers, or externally, through a supplied
clock. An internally generated clock is a divide down of the clockout frequency,
f(H1). A continuous transfer mode is available, which allows the serial port to
transmit and receive any number of words without new synchronization pulses.
Eight memory-mapped registers are provided for each serial port:
- Global-control register
- Two control registers for the six serial I/O pins
- Three receive/transmit timer registers
- Data-transmit register
- Data-receive register
The global-control register controls the global functions of the serial port and
determines the serial-port operating mode. Two port control registers control
the functions of the six serial port pins. The transmit buffer contains the next
complete word to be transmitted. The receive buffer contains the last complete
word received. Three additional registers are associated with the transmit/
receive sections of the serial-port timer. A serial-port block diagram is shown
in Figure 12–11 on page 12-16, and the memory map of the serial ports is
shown in Figure 12–12 on page 12-17.