Serial Interface Signals - Motorola DragonBall MC68328 User Manual

SECTION 8
UNIVERSAL ASYNCHRONOUS RECEIVER/
TRANSMITTER (UART)
The universal asynchronous receiver/transmitter (UART) provides serial communication
with external devices such as modems and other computers. Data is transported in charac-
ter blocks at data rates ranging from 300 bps to over 1 Mbps using a standard "start-stop"
format. Some of the key features of the UART include:
• Full duplex operation
• Flexible 5-wire serial interface
• Direct support of IrDA physical layer protocol
• Robust receiver data sampling with noise filtering
• 8-byte FIFOs for transmit and receive
• 7-, 8-bit operation with optional parity
• Generation and break detection
• Baud-rate generator
• Flexible clocking options
• Standard baud rates 300bps to 115.2kbps with 16x sample clock
• External 1x clock for high-speed synchronous communication
• Programmer's model optimized for 16-bit bus
• 8 maskable interrupts
• Low-power idle mode
The UART performs all normal operations associated with start-stop asynchronous commu-
nication. Serial data is transmitted and received at standard bit rates using the internal baud-
rate generator. For those applications that need other bit rates, a 1x clock mode is available
where users provide the data-bit clock. Figure 8-1 shows a high-level block diagram of the
module.

8.1 SERIAL INTERFACE SIGNALS

There are 5 signals accessible to users and are described below. If users need any or all
UART signals, the appropriate port bits can be programmed to assume their UART function.
Refer to Section 7 Parallel Ports for information about programming the ports.
MOTOROLA MC68328 DRAGONBALL PROCESSOR USER'S MANUAL 8-1