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Notes
79RC32438 User Reference Manual
13 - 1
November 4, 2002
Chapter 13
UART Controller
Introduction
The RC32438 contains two completely separate but identical serial channels (UARTs). Each UART is
compatible with the industry standard 16550
1
UART. The two UARTs (referred to as channel 0 and channel
1) are functionally identical, except UART channel 1 does not use all the available modem control pins.
Features
Compatible with the 16550 and 16450 UARTs
Two completely separate serial channels
Modem control functions (CTS, RTS, DSR, DTR, RI, DCD)
16-byte transmit and receive buffers
Programmable baud rate generator derived from the system clock
Fully programmable serial characteristics:
5, 6, 7, or 8 bit characters
Even, odd or no parity bit generation and detection
1, 1-1/2 or 2 stop bit generation
Line break generation and detection
False start bit detection
Internal loopback mode
Functional Overview
The 16550 UART is an enhanced version of the 16450 UART. Upon power-up, each UART defaults to
the 16450 mode. The 16550 contains two 16-byte buffers: one in the receive data path and one in the
transmit data path. The buffers reduce the overhead on the CPU core in managing the data flow. The 16450
does not use the buffers in the data path.
The CPU core can read the status of either UART channel at any time during operation. Status informa-
tion that is available includes the type and condition of the transfer operation, as well as any error condition
(parity, overrun, framing, or break interrupt). The baud rate generator divides down the IPBus clock and
provides a 16X clock for driving the transmitter and receiver logic.
The UART pins shown in Table 13.1 are multiplexed with the GPIO pins as shown in Table 12.1.
1.
PC 16550D Dual Universal Asynchronous Receiver/Transmitter with FIFOs
, June 1995, National Semicon-
ductor
.
Signal
Description
Direction
U0SOUT
UART Channel 0 Serial Output
Output
U0SINP
UART Channel 0 Serial Input
Input
U0RIN
UART Channel 0 Ring Indicator
Input
U0DCRN
UART Channel 0 Data Carrier Detect
Input
U0DTRN
UART Channel 0 Data Terminal Ready
Output
U0DSRN
UART Channel 0 Data Set Ready
Input
Table 13.1 UART Input/Output Pins (Part 1 of 2)