[31:2]
Reserved
UART Interrupt Pending Register (
ip
)
Register Offset
0x14
Bits
Field Name
Attr.
Rst.
Description
0
txwm
RO
X
Transmit watermark interrupt pending
1
rxwm
RO
X
Receive watermark interrupt pending
[31:2]
Reserved
The read-write,
div_width
-bit
div
register specifies the divisor used by baud rate generation
for both Tx and Rx channels. The relationship between the input clock and baud rate is given by
the following formula:
The input clock is the bus clock
tlclk
. The reset value of the register is set to
div_init
, which
is tuned to provide a 115200 baud output out of reset given the expected frequency of
tlclk
.
Table 61 shows divisors for some common core clock rates and commonly used baud rates.
Note that the table shows the divide ratios, which are one greater than the value stored in the
div
register.
Table 61:
Common baud rates (MIDI=31250, DMX=250000) and required
divide values to achieve them with given bus clock frequencies. The divide val-
ues are one greater than the value stored in the
div
register.
tlclk
(MHz)
Target Baud (Hz)
Divisor
Actual Baud (Hz)
Error (%)
2
31250
64
31250
0
2
115200
17
117647
2.1
16
31250
512
31250
0
16
115200
139
115107
0.08
16
250000
64
250000
0
Table 59:
UART Interrupt Enable Register
Table 60:
UART Interrupt Pending Register
Chapter 17 Universal Asynchronous Receiver/Transmitter
FE310-G003 Manual
© SiFive, Inc.
Page 85
Содержание FE310-G003
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