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IDT UART Controller
UART Register Description
79RC32438 User Reference Manual
13 - 2
November 4, 2002
Notes
The UART must be configured before operation may begin. To configure the UART:
1. Set up the transmit and receive parameters in the line control (UARTxLC) register.
2. Program the baud rate in the divisor latch low (UARTDLL) and divisor latch high (UARTDLH) regis-
ters.
3. Enable, if desired, the 16550 buffer mode in the FIFO control (UARTxFC) register.
The general purpose I/O controller must be configured to use the desired UART pins as alternate func-
tion GPIO pins. The UART contains a baud rate generator which is used to operate the transmit and receive
logic at the baud rate determined by the divisor latches.
UART Register Description
In order to maintain full compatibility with the 16550, all registers in the UART are 8-bits in size and have
the addressing architecture of the 16550. Despite the fact that the registers are 8-bits in size, they are word
aligned. As in the 16550, the exact register which is selected when accessing the UART is dependent on
the divisor latch access bit (DLAB) in the line control (UARTxLC) register and on whether a read or write
operation is performed. Table 13.2 lists the UART registers.
U0RTSN
UART Channel 0 Request to Send
Output
U0CTSN
UART Channel 0 Clear to Send
Input
U1SOUT
UART Channel 1 Serial Output
Output
U1SINP
UART Channel 1 Serial Input
Input
U1DTRN
UART Channel 1 Data Terminal Ready
Output
U1DSRN
UART Channel 1 Data Set Ready
Input
U1RTSN
UART Channel 1 Request to Send
Output
U1CTSN
UART Channel 1 Clear to Send
Input
Register
Offset
Register Name
Register Function
Size
DLAB = 0
DLAB = 1
0x05_0000
UART0RB (read)
UART0TH (write)
UART0DLL
UART 0 receive buffer / UART 0 trans-
mit holding / UART 0 divisor latch low
32-bit
0x05_0004
UART0IE
UART0DLH
UART 0 interrupt enable / UART 0 divi-
sor latch high
32-bit
0x05_0008
UART0II (read)
UART0FC (write)
none
UART 0 interrupt identification / UART
0 FIFO control
32-bit
0x05_000C
UART0LC
UART 0 line control
32-bit
0x05_0010
UART0MC
UART 0 modem control
32-bit
0x05_0014
UART0LS
UART 0 line status
32-bit
0x05_0018
UART0MS
UART 0 modem status
32-bit
0x05_001C
UAART0S
UART 0 scratch
32-bit
0x05_0020
UART1RB (read)
UART1TH (write)
UART1DLL
UART 1 receive buffer / UART 1 trans-
mit holding / UART 1 divisor latch low
32-bit
0x05_0024
UART1IE
UART1DLH
UART 1 interrupt enable / UART 1 divi-
sor latch high
32-bit
Table 13.2 UART Register Map (Part 1 of 2)
Table 13.1 UART Input/Output Pins (Part 2 of 2)