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UM10850
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User manual
Rev. 2.4 — 13 September 2016
344 of 464
NXP Semiconductors
UM10850
Chapter 24: LPC5410x System FIFO for Serial Peripherals
24.5.7 Configuration register for USARTn
The CFGUSART register allows configuration of the transmit and receive FIFO thresholds
and the receive FIFO timeout. Each USART has a dedicated CFGUSART register.
24.5.7.1 Receiver Timeout
A single 19-bit timeout timer is used for all receiver FIFOs. TimeoutBase chooses a bit of
that timer to be used as the place to begin comparing the timer to TimeoutValue, from bit 0
up to bit 15. The compare is always 4 bits in size. TimeoutValue can be any value from 2
to 15. This gives a maximum timeout range of 2 counts (too small to be useful) at the
bottom end, up to 15 * 32,768 (491,520) counts at the upper end. TimeoutValue of 0 and 1
should not be used. The timeout is enabled for each peripheral when the related interrupt
is enabled.
Table 382. Address map CFGUSART[0:3] registers
Peripheral
Base address
Offset
Increment
Dimension
VFIFO
0x1C03 8000
[0x1100:0x1300]
0x100
4
Table 383. Configuration register for USARTn (CFGUSART[0:3], address offset [0x1000:0x1300]) bit description
Bit
Symbol
Description
Reset Value
3:0
-
Reserved. Read value is undefined, only zero should be written.
NA
4
TIMEOUT
CONT
ONWRITE
Timeout Continue On Write. When 0, the timeout for the related peripheral is reset
every time data is transferred from the peripheral into the receive FIFO.
When 1, the timeout for the related peripheral is not reset every time data is
transferred into the receive FIFO. This allows the timeout to be applied to
accumulated data, perhaps related to the FIFO threshold.
0
5
TIMEOUT
CONT
ONEMPTY
Timeout Continue On Empty. When 0, the timeout for the related peripheral is reset
when the receive FIFO becomes empty.
When 1, the timeout for the related peripheral is not reset when the receive FIFO
becomes empty. This allows the timeout to be used to flag idle peripherals, and could
potentially be used to indicate the end of a transmission of indeterminate length.
0
7:6
-
Reserved. Read value is undefined, only zero should be written.
NA
11:8
TIMEOUT
BASE
Specifies the least significant timer bit to compare to TimeoutValue. See
below. Value can be 0 through 15.
0
15:12 TIMEOUT
VALUE
Specifies the maximum time value for timeout at the timer position identified by
TimeoutBase. Minimum time TimeoutValue - 1 (clocks of wdt_clk). See
below. TimeoutValue should not be 0 or 1 when timeout is enabled.
0
23:16 RX
THRESHOLD
Receive FIFO Threshold. The System FIFO indicates that the threshold has been
reached when the number of entries in the receive FIFO is greater than this value.
For example, when RxThreshold = 0, the threshold is exceeded when there is at least
one entry in the receive FIFO.
An interrupt can be generated when the RxThreshold has been reached (see
), but has no effect on DMA requests, which are generated whenever
the receiver FIFO is not empty.
0
31:24 TX
THRESHOLD
Transmit FIFO Threshold. The System FIFO indicates that the threshold has been
reached when the number of free entries in the transmit FIFO is less than or equal to
this value. For example, when TxThreshold = 0, the threshold is exceeded when
there is at least one free entry in the transmit FIFO.
An interrupt can be generated when the TxThreshold has been reached (see
), but has no effect on DMA requests, which are generated whenever
the transmit FIFO has any free entries.
0