Uart1 with hdlc and modem control signals, 1 introduction, 2 uart overview – Cirrus Logic EP93xx User Manual
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Copyright 2007 Cirrus Logic
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Chapter 14
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UART1 With HDLC and Modem Control Signals
14.1 Introduction
UART1 is the collection of a UART block along with a block to support a 9 pin modem
interface and a block to support synchronous and asynchronous HDLC protocol support for
full duplex transmit and receive. The following sections address each of these blocks.
14.2 UART Overview
Transmit and Receive data transfers through UART1 can either be managed by the DMA,
interrupt driven, or CPU polled operations. A loopback control bit is available to enable
system testing by routing the transmit data stream into the receiver.
The UART performs:
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Serial-to-parallel conversion on data received from a peripheral device.
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Parallel-to-serial conversion on data transmitted to the peripheral device.
The CPU reads and writes data and control/status information via the AMBA APB interface.
The transmit and receive paths are buffered with internal FIFO memories allowing up to
16 bytes to be stored independently in both transmit and receive modes.
The UART:
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Includes a programmable baud rate generator which generates a common transmit and
receive internal clock from the UART internal reference clock input, UARTCLK.
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Offers similar functionality to the industry-standard 16C550 UART device.
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Supports baud rates of up to 115.2 Kbps and beyond, subject to UARTCLK reference
clock frequency.
The UART operation and baud rate values are controlled by the line control register
(UART1LinCtrl).
The UART can generate:
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Four individually-maskable interrupts from the receive, transmit and modem status logic
blocks.
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A single combined interrupt so that the output is asserted if any of the individual
interrupts are asserted and unmasked.
If a framing, parity or break error occurs during reception, the appropriate error bit is set, and
is stored in the FIFO. If an overrun condition occurs, the overrun register bit is set
immediately and FIFO data is prevented from being overwritten.