UM10503
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User manual
Rev. 1.3 — 6 July 2012
969 of 1269
NXP Semiconductors
UM10503
Chapter 37: LPC43xx USART0_2_3
37.6.18 USART RS485 Delay value register
The user may program the 8-bit RS485DLY register with a delay between the last stop bit
leaving the TXFIFO and the de-assertion of the DIR pin. This delay time is in periods of
the baud clock. Any delay time from 0 to 255 bit times may be programmed.
37.6.19 USART Synchronous mode control register
SYNCCTRL register is a Read/write register that controls the synchronous mode. The
synchronous mode control module generates or receives the synchronous clock with the
serial input/ output data and distributes the edge detect samples to the transmit and
receive shift registers.
Table 842. USART RS485 Delay value register (RS485DLY - addresses 0x4008 1054
(USART0), 0x400C 1054 (USART2), 0x400C 2054 (USART3)) bit description
Bit
Symbol
Description
Reset value
7:0
DLY
Contains the direction control delay value. This register works in
conjunction with an 8-bit counter.
0x00
31:8
-
Reserved, user software should not write ones to reserved bits.
The value read from a reserved bit is not defined.
NA
Table 843. USART Synchronous mode control registers (SYNCCTRL - address addresses
0x4008 1058 (USART0), 0x400C 1058 (USART2), 0x400C 2058 (USART3)) bit
description
Bit
Symbol
Value
Description
Reset
value
0
SYNC
Enables synchronous mode.
0
0
Disabled
1
Enabled
1
CSRC
Clock source select.
0
0
Synchronous slave mode (SCLK in)
1
Synchronous master mode (SCLK out)
2
FES
Falling edge sampling.
0
0
RxD is sampled on the rising edge of SCLK.
1
RxD is sampled on the falling edge of SCLK.
3
TSBYPASS
Transmit synchronization bypass in synchronous slave
mode.
0
0
The input clock is synchronized prior to being used in
clock edge detection logic.
1
The input clock is not synchronized prior to being used
in clock edge detection logic. This allows for a high er
input clock rate at the expense of potential metastability.
4
CSCEN
Continuous master clock enable (used only when
CSRC is 1)
0
0
SCLK cycles only when characters are being sent on
TxD.
1
SCLK runs continuously (characters can be received on
RxD independently from transmission on TxD).