LS_Universal asynchronous receiver/transmitter (UART)
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27.4.4 UARTIBRD
register
The UARTIBRD (integer baud rate) is a 16 bit RW register which indicates the integer part of
the baud rate divisor value. The UARTIBRD bit assignments are given in
.
27.4.5 UARTFBRD
register
The UARTFBRD (fractional baud rate) is a 6 bit RW register which indicates the fractional
part of the baud rate divisor value. The UARTFBRD bit assignments are given in
The baud rate divisor is calculates as follows:
BAUDDIV = f
UARTCLK
/ (16 · baud rate)
where f
UARTCLK
is the UART reference clock frequency. The BAUDDIV is comprised of the
integer value BAUD DIVINT and the fractional value BAUD DIVFRAC.
Note:
The contents of UARTIBRD and UARTFBRD registers are not update until transmission or
reception of the current character is complete.
Note:
The minimum divide ratio is 1 and the maximum is 65535 (that is, 216-1). When UARTIBRD
= 65535 (16‘hFFFF), UARTFBRD must not be greater than zero.
Some typical bit rates and their corresponding integer divisors (BAUD DIVINT in
UARTIBRD) are given in
[01]
DSR
1’h0
Data set ready.
This bit is set to 1‘b1 when the modem status input is 1‘b0
(
). Specifically, it is the complement of the UART
data carrier detect nUARTDSR modem status input.
[00]
CTS
1’h0
Clear to send.
This bit is set to 1‘b1 when the modem status input is 1‘b0
(
). Specifically, it is the complement of the UART
clear to send nUARTCTS modem status input.
Table 524.
UARTFR register bit assignments (continued)
Bit
Name
Reset value Description
Table 525.
UARTIBRD register bit assignments
Bit
Name
Reset value Description
[15:00]
BAUD DIVINT
16’h0
Integer baud rate divisor.
Table 526.
UARTFBRD register bit assignments
Bit
Name
Reset value Description
[05:00]
BAUD DIVFRAC
6’h0
Fractional baud rate divisor.