Uart Interfaces; Overview - Intel PXA27 Series Design Manual

UART Interfaces

This chapter describes guidelines to interface to the Universal Asynchronous Receiver/Transmitter
(UART) serial ports of Intel
10.1

Overview

The PXA27x processor has three UARTs:
•
A Full Function UART (FFUART)
•
A Bluetooth
•
A standard UART (STUART)
All the UARTs use the same programming model.
The serial ports are controlled using direct memory access (DMA) or programmed I/O. Each serial
port contains a UART and a slow infrared transmit encoder and receive decoder that conforms to
the IrDA Serial Infrared (SIR) Physical Layer Link Specification.
Each UART performs serial-to-parallel conversion on data characters received from a peripheral
device or a modem and parallel-to-serial conversion on data characters received from the
processor. The processor reads the complete status of a UART during functional operation. Status
information includes the type and condition of transfer operations and error conditions (parity,
overrun, framing, or break interrupt) associated with the UART.
Each serial port operates in FIFO or non-FIFO mode. In FIFO mode, a 64-byte transmit FIFO
holds data from the processor until it is transmitted on the serial link and a 64-byte receive FIFO
buffers data from the serial link until it is read by the processor. In non-FIFO mode, the transmit
and receive FIFOs are bypassed.
Each UART includes a programmable baud rate generator that divides the input clock by 1 to (2
1). This produces a 16X clock that drives the internal transmitter and receiver logic. Software
programs interrupts to meet its requirements. This minimizes the number of computations required
to handle the communications link. Each UART operates in an environment which is controlled by
software and is polled or interrupt driven.
All three UARTs support the 16550A
features supported by each of the three UARTs.
1. Bluetooth is trademarked by the Bluetooth SIG Inc. U.S.A. See the Bluetooth SIG Internet site at http://www.bluetooth.com.
2. The 16550A was originally produced by National Semiconductor Inc.
3. The 16750 is produced as the TL16C750 by Texas Instruments.
®
Intel PXA27x Processor Family Design Guide
®
PXA27x Processor Family (PXA27x processor).
1
UART (BTUART)
2
and 16750
3
functions, but are slightly different in regard to
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