UM10503
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© NXP B.V. 2015. All rights reserved.
User manual
Rev. 2.1 — 10 December 2015
1151 of 1441
NXP Semiconductors
UM10503
Chapter 40: LPC43xx/LPC43Sxx USART0_2_3
ISO 7816 class A, B, or C power requirements, be aware of the logic level tolerances and
requirements when communicating or powering cards that use different power rails than
this part.
40.7.6.1 Smart card set-up procedure
A T = 0 protocol transfer consists of 8-bits of data, an even parity bit, and two guard bits
that allow for the receiver of the particular transfer to flag parity errors through the NACK
response (see
). Extra guard bits may be added according to card
requirements. If no NACK is sent (provided the interface accepts them in SCICTRL), the
next byte may be transmitted immediately after the last guard bit. If the NACK is sent, the
transmitter will retry sending the byte until successfully received or until the SCICTRL
retry limit has been met.
The smart card must be set up with the following considerations:
1. If necessary, bring the USART out of reset and enable clocking to the peripheral.
2. Setup an available USART TXD pin for the bidirectional transfers.
3. Set up the UCLK pin as the clock source using pin configuration registers. The default
clock requirement for most asynchronous cards is 372 times the bit rate.
4. Configure DLL and DLM for baud rate. It may not be necessary to target a specific
standard baud rate but rather to maintain a fraction of the previously mentioned clock
rate. For example if the clock rate is set to 4 MHz the baud rate would be 10753. A
clock rate of 3.5712 MHz would need a baud rate of 9600. An ISO 7816 PPS
exchange may require the baud rate to be changed later.
5. Configure LCR for character size and parity (typically 8-bit and even parity).
6. Configure SCICTRL with the desired NACK response, extra guard bits, and protocol
type.
7. Place the GPIO output signals into an inactive state where card power is off, RST is
low, and CLK is low and unchanging.
Thereafter, software should monitor card insertion, handle activation, wait for answer to
reset as described in ISO7816-3.
Fig 131. Smart card T = 0 waveform
start
bit0
bit1
bit2
bit3
bit4
bit5
bit6
bit7
parity
NACK
guard1 guard2
extra
guard1
extra
guard2
extra
guard
n
start
bit0
Asynchronous transfer
Next transfer or
First retry
TXD
Clock