Iso-7816/Smartcard Support - NXP Semiconductors MKL27Z128VFM4 Reference Manual

Table of Contents

Functional description

Figure 38-23. Loop operation (C1[LOOPS] = 1, C1[RSRC] = 0)

Enable loop operation by setting C1[LOOPS] and clearing C1[RSRC]. Setting

C1[LOOPS] disables the path from the unsynchronized receiver input signal to the

receiver. Clearing C1[RSRC] connects the transmitter output to the receiver input. Both

the transmitter and receiver must be enabled (C2[TE] = 1 and C2[RE] = 1). When

C7816[ISO_7816EN] is set, it is not required that both C2[TE] and C2[RE] are set.

38.5.7 ISO-7816/smartcard support

The UART provides mechanisms to support the ISO-7816 protocol that is commonly

used to interface with smartcards. The ISO-7816 protocol is an NRZ, single wire, half-

duplex interface. The TxD pin is used in open-drain mode because the data signal is used

for both transmitting and receiving. There are multiple subprotocols within the ISO-7816

standard. The UART supports both T = 0 and T = 1 protocols. The module also provides

for automated initial character detection and configuration, which allows for support of

both direct convention and inverse convention data formats. A variety of interrupts

specific to 7816 are provided in addition to the general interrupts to assist software.

Additionally, the module is able to provide automated NACK responses and has

programmed automated retransmission of failed packets. An assortment of programmable

timeouts and guard band times are also supported.

The term elemental time unit (ETU) is frequently used in the context of ISO-7816. This

concept is used to relate the frequency that the system (UART) is running at and the

frequency that data is being transmitted and received. One ETU represents the time it

takes to transmit or receive a single bit. For example, a standard 7816 packet, excluding

any guard time or NACK elements is 10 ETUs (start bit, 8 data bits, and a parity bit).

Guard times and wait times are also measured in ETUs.,

The ISO-7816 specification may have certain configuration

options that are reserved. To maintain maximum flexibility to

support future 7816 enhancements or devices that may not

strictly conform to the specification, the UART does not

prevent those options being used. Further, the UART may

KL27 Sub-Family Reference Manual , Rev. 5, 01/2016

Tx pin output

Freescale Semiconductor, Inc.