![NXP Semiconductors LPC43Sxx User Manual Download Page 1137](http://html1.mh-extra.com/html/nxp-semiconductors/lpc43sxx/lpc43sxx_user-manual_17218271137.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
1137 of 1441
NXP Semiconductors
UM10503
Chapter 40: LPC43xx/LPC43Sxx USART0_2_3
The NACKDIS bit is used to inhibit a nack response during T=0 (the I/O line is not pulled
low during the guard time to indicate an erroneous reception). The received character will
be stored in the RX FIFO but a parity error will be generated. It is up to the software to
handle the incorrect received character.
The PROTSEL bit is used to selected between the two supported smart card protocols
T=0 and T=1. More information on these protocols can be found in the ISO 7816-3
standard.
The retry bit field indicates the number of retransmission when receiving a NACK
response, which can be up to 7 trails. When the number is exceeded, an interrupt is
generated and the USART is locked until the FIFO is empty. This can be done by flushing
the FIFO. When no FIFO is available, or the FIFO is already empty, the interrupt can be
used by the software to determine the next action.
The guard time bit file is used to program the extra number of guard time cycles to allow
the smart card to process the information before sending a response. The extra guard
time can be programmed from 0 to 255, where 255 indicates the minimum possible
character length. This value is depending on the selected protocol and can be either 11
etu for protocol T=1 or 12 etu for protocol T=0.
Waiting times as defined in the standard cannot be programmed directly, but are
implemented using the capture inputs of the timers.
Remark:
The SCICTRL register should not be modified while sending or receiving data,
or data may be lost or corrupted.
Remark:
The SCICTRL register should not be enabled in combination with the
SYNCCTRL register, as only asynchronous smart card is supported.
40.6.16 USART RS485 Control register
The RS485CTRL register controls the configuration of the USART in RS-485/EIA-485
mode.
Table 943. USART RS485 Control register (RS485CTRL, addresses 0x4008 104C (USART0),
0x400C 104C (USART2), 0x400C 204C (USART3)) bit description
Bit
Symbol
Value
Description
Reset
value
0
NMMEN
NMM enable.
0
0
Disabled. RS-485/EIA-485 Normal Multidrop
Mode (NMM) is disabled.
1
Enabled. RS-485/EIA-485 Normal Multidrop
Mode (NMM) is enabled. In this mode, an address
is detected when a received byte causes the
USART to set the parity error and generate an
interrupt.
1
RXDIS
Receiver enable.
0
0
Enabled. The receiver is enabled.
1
Disabled.The receiver is disabled.