Features; Functional Descriptions; Elementary Time Unit Counter - Holtek HT32F52342 User Manual

32-Bit Arm ® Cortex ® -M0+ MCU
HT32F52342/HT32F52352

Features

▄
Supports ISO 7816-3 standard
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Character Transfer Mode
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1 transmit buffer and 1 receive buffer
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11-bit ETU (elementary time unit) counter
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9-bit guard time counter
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24-bit general purpose waiting time counter
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Parity generation and checking
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Automatic character repetition on parity error detection in transmission and reception modes
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Supports PDMA access at a transmission or reception completion

Functional Descriptions

To communicate with an external Smart Card, the integrated Smart Card Interface has a series
of external pins known as SCI_CLK, SCI_DIO and SCI_DET. The SCI_CLK pin is the clock
output signal used to communicate with the external Smart Card together with the serial data pin
named SCI_DIO. The operation of the SCI_CLK and SCI_DIO pins can be selected to be the SCI
data Transfer Mode which is driven automatically by the SCI control circuits or to be the Manual
mode which is controlled by configuring the internal CLK and DIO register bits respectively by
the application program. The SCI_DET pin is the external card detection input pin. Insertion or
removal of the external Smart Card can be automatically detected and generate an interrupt signal
which is sent to the microcontroller if the corresponding interrupt function is enabled.
For proper data transfer, some timing related procedures must be executed before the Smart
Card Interface can begin to communicate with the external card. There are three counters named
Elementary Time Unit, ETU, Guard Time Counter, GT, and Waiting Time Counter, WT, which are
used for the timing related functions in Smart Card Interface data transfer operations.

Elementary Time Unit Counter

The Elementary Time Unit, ETU, is an 11-bit up-counting counter which generates a clock
denoted as f
ETU
reception. The clock source of the ETU comes from the Smart Card clock, named f
derived from the 6-bit prescaler. The data transfer of the SCI is a character frame based protocol,
which basically consists of a Start bit, 8-bits of data and a Parity bit. The time period, t
f ), generated by the ETU, is the time unit for a character bit. There is a register related to the
ETU
Elementary Time Unit known as the ETUR register which stores the expected contents of the
ETU. Each time the ETUR register is written, the ETU circuitry will reload the new written value
and restart counting. The elementary time unit t
defines the bit rate in the ISO 7816-3 standard specification.
Rev. 1.30
to be used as the operating frequency source for the SCI data transmission and
1etu = t
539 of 656
is obtained from the following formula which
ETU
F
1
= ×
i
ETU
D
f
i
, which is
PSC_CK
(1/
ETU
September 28, 2018