MPC8540 datasheet(481/1302 Pages) FREESCALE

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External Signal Descriptions

MPC8540 PowerQUICC III Integrated Host Processor Reference Manual, Rev. 1

Freescale Semiconductor

12-3

•

Internal diagnostic support, local loopback, and break functions

•

Prioritized interrupt reporting

•

Overrun, parity, and framing error detection

12.1.2 Modes of Operation

The communication channel provides a full-duplex asynchronous receiver and transmitter using

an operating frequency derived from the CCB clock.

The transmitter accepts parallel data from a write to the transmitter holding register (UTHR). In

FIFO mode, the data is placed directly into an internal transmitter shift register of the transmitter

FIFO. The transmitter converts the data to a serial bit stream inserting the appropriate start, stop,

and optional parity bits. Finally, it outputs a composite serial data stream on the channel transmitter

serial data output signal (SOUT). The transmitter status may be polled or interrupt driven.

The receiver accepts serial data bits on the channel receiver serial data input signal (SIN), converts

it to parallel format, checks for a start bit, parity (if any), stop bits, and transfers the assembled

character (with start, stop, parity bits removed) from the receiver buffer (or FIFO) in response to

a read of the UART’s receiver buffer register (URBR). The receiver status may be polled or

interrupt driven.

12.2 External Signal Descriptions

This section contains a signal overview and detailed signal descriptions.

12.2.1 Signal Overview

Table 12-1 summarizes the DUART signals. Note that although the actual device signal names are

prepended with the UART_ prefix as shown in the table, the functional (abbreviated) signal names

are often used throughout this chapter.

12.2.2 Detailed Signal Descriptions

The eight DUART signals are described in detail in Table 12-2.

Table 12-1. DUART Signal Overview

Signal Name

I/O

Pins

Reset

Value

State Meaning

UART_SIN[0:1]

Serial in data UART0 and UART1

UART_SOUT[0:1]

Serial out data UART0 and UART1

UART_CTS[0:1]

Clear to send UART0 and UART1

UART_RTS[0:1]

Request to send UART0 and UART1

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