UARTs
LH79524/LH79525 User’s Guide
16-2
Version 1.0
16.1 Theory of Operation
The three UARTs, UART0, UART1, and UART2, offer similar functionality to the industry-
standard 16C550. They perform serial-to-parallel conversion on data received from a
peripheral device and parallel-to-serial conversion on data transmitted to the UART.
The CPU reads and writes data and control/status information through the AMBA APB
interface. The transmit and receive paths are buffered with internal FIFO memories that
support programmable ‘watermark levels’, and overrun protection. These FIFO memories
enable up to 32 entries to be stored independently in both transmit and receive
modes. All UART Control and Status Registers can be accessed through the APB.
Figure 16-1. UART0, UART1, and UART2 Block Diagram
LH79525-63
APB
INTERFACE
AND
REGISTER
BLOCK
BAUD
RATE
GENERATOR
TRANSMITTER
32 × 12
RECEIVE
FIFO
BAUD16
RECEIVER
INTERRUPT
GENERATION
DMA
INTERFACE
TRANSMIT
FIFO
STATUS
FIFO
FLAGS
RECEIVE
FIFO
STATUS
32 × 9
TRANSMIT
FIFO
SYSTEM CLOCK
nUARTRST
PRESETn
PSEL
UARTRXDMACLR
REFERENCE CLOCK
UARTCLK
nUARTCTS
UARTTXDMACLR
UARTRXDMABREQ
UARTTXDMABREQ
UARTINTR
nUARTRTS
PENABLE
PWRITE
BAUD RATE
DIVISOR
CONTROL AND STATUS
PADDR[11:2]
PWDATA[15:0]
WRITE
DATA
TxD
RxD
UARTTXD
UARTIRTX
UARTRXD
UARTIRRX
READ
DATA[11:0]
PRDATA[15:0]