Élan™SC520 Microcontroller User’s Manual 21-1
CHAPTER
21
UART SERIAL PORTS
21.1 OVERVIEW
The ÉlanSC520 microcontroller includes two industry-standard 16550-compatible UARTs,
both capable of running all existing 16450 and 16550 software.
The UARTs power up in 16450-compatible UART mode (also called
character mode
or
non-FIFO
mode). Each UART can be switched between the 16550-compatible mode (also
called
FIFO mode
) and 16450-compatible mode under software control. In 16550-
compatible mode, the receiver and the transmitter are each buffered with 16-byte FIFOs
to offload the CPU from repetitive service routines.
Features:
■ Full UART pinout: SOUT, SIN, CTS, RTS, DSR, DTR, RIN, and DCD for each UART
■ In 16550-compatible mode, the transmitter and receiver are each buffered with 16-byte
FIFOs
■ Full-duplex (data can be sent in both directions simultaneously)
■ DMA operation
■ Internal baud-rate clock of 18.432 MHz or 1.8432 MHz
■ Baud rates from DC to 1.152 Mbaud
– Baud-rate generator provides input clock divisor from 1 to (2
16
–1) to create 16x clock.
■ Programmable serial interface:
– 5-, 6-, 7-, and 8-bit character sizes
– Even, odd, or no-parity bit generation and detection
– 1, 1½, or 2 stop bits
– Break generation and detection
– Each UART’s address decode can be individually disabled, allowing external devices
to be used in their place.
■ Internal Diagnostics:
– False start bit detection
– Complete status reporting capabilities
– Break, parity error, overrun error, and framing error detection
– Loopback controls for communications link fault isolation
21.2 BLOCK DIAGRAM
Figure 21-1 shows a block diagram of a single UART. The ÉlanSC520 microcontroller
includes two UARTS that function identically to each other.
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