![NXP Semiconductors LPC43Sxx Скачать руководство пользователя страница 1148](http://html1.mh-extra.com/html/nxp-semiconductors/lpc43sxx/lpc43sxx_user-manual_17218271148.webp)
UM10503
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2015. All rights reserved.
User manual
Rev. 2.1 — 10 December 2015
1148 of 1441
NXP Semiconductors
UM10503
Chapter 40: LPC43xx/LPC43Sxx USART0_2_3
The RS485CTRL bit 4 takes precedence over all other mechanisms controlling the
direction control pin.
RS485/EIA-485 driver delay time
The driver delay time is the delay between the last stop bit leaving the TXFIFO and the
de-assertion of the DIR pin. This delay time can be programmed in the 8-bit RS485DLY
register. The delay time is in periods of the baud clock. Any delay time from 0 to 255 bit
times may be used.
RS485/EIA-485 output inversion
The polarity of the direction control signal on the DIR pin can be reversed by programming
bit 5 in the RS485CTRL register. When this bit is set, the direction control pin will be
driven to logic 1 when the transmitter has data waiting to be sent. The direction control pin
will be driven to logic 0 after the last bit of data has been transmitted.
40.7.5 Synchronous mode
When the synchronous receiver/ transmitter feature is configured (USART), the serial
interface is extended with a serial input and output clock and an output enable for
controlling the clock pad.
By default transmission and reception in synchronous mode operates uses the same
protocol as in asynchronous mode. Synchronous mode can be configured using the
Synchronous Mode Control Register. This register allows to control:
•
The direction of the serial clock, i.e. synchronous slave or master mode
•
The sampling edge of the serial clock
•
Two-stage or one stage synchronization of the input serial clock during transmission
•
During synchronous master mode, the clock can be continuous or disabled when in
idle or break mode
•
The transmission of start and stop bits can be omitted. Valid data is identified by a
running clock. Sampling is always done on the falling edge of the serial clock
Data is shifted in the receive shift register at the sampling edge of the serial clock.
40.7.5.1 USART clock in synchronous mode
In synchronous master mode, the USART synchronous clock is determined as follows:
(9)
DLM and DLL are the standard USART0 baud rate divider registers, and DIVADDVAL and
MULVAL are USART0 fractional baud rate generator specific parameters. Setting
DIVADDVAL = 0 disables the fractional baud rate generator.
Un
_UCLK
BASE_UARTn_CLK
2
256
DLM
DLL
+
1
DIVADDVAL
MULVAL
-----------------------------------
+
----------------------------------------------------------------------------------------------------------------------
=