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Serial Communication Modules
16-2
MPC801 USER’S MANUAL
MOTOROLA
16
16.1.1 Features
The following list summarizes the main features of the UART controllers:
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- and 8-Bit Operation with Optional Parity
Generation and Detection of Break
Baud Rate Generator
Flexible Clocking Options
Standard Baud Rates of 300bps to 115.2kbps with a 16
External 1
×
clock for High-Speed Synchronous Communication
Eight Maskable Interrupts
Optional Low-Power Idle Mode
×
Sample Clock
16.2 SERIAL INTERFACE SIGNALS
You can access the following signals, which become default signals after reset. If you do not
need any UART signals, program the appropriate port as an I/O.
Transmit Data (TXD)—This pin is the transmitter serial output. While in normal mode,
Non Return to Zero (NRZ) data is output. While in IrDA mode, a 3- or 16-bit period pulse
is output for each “zero” bit transmitted. For RS-232 applications, this pin must be
connected to an RS-232 transmitter. For infra-red applications this pin can directly drive
an infra-red LED.
Clear to Send (CTS)—This active low input is used to control the transmitter. Normally,
the transmitter waits until this signal is active (low) before a character is transmitted. If
the ICTS bit of the transmitter register is set, the transmitter sends a character
whenever one is ready to transmit. This pin can then be used as a general-purpose
input whose status is read in the CTSS bit of the transmitter register. It can post an
interrupt on any transition of this pin if the interrupt is enabled.
Receive Data (RXD)—This pin is the receiver serial input. While in normal operation,
NRZ data is expected. However, while in infra-red mode, a narrow pulse is expected for
each “zero” bit received. External circuitry must be used to convert the infra-red signal
to an electrical signal. RS-232 applications need an external RS-232 receiver to convert
from RS-232 voltage levels.