AN2284 datasheet(11/40 Pages) STMICROELECTRONICS

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AN2284

4 SC Peripheral Description

11/40

Figure 1.

ISO 7816-3 Asynchronous Protocol

4.4

Smart Card Clock Generator

The SmartCard clock generator provides a clock signal to the connected SmartCard. The

SmartCard uses this clock to derive the baud rate clock for the serial I/O between the

SmartCard and another UART. The clock is also used for the CPU in the card, if present.

Operation of the Smart Card interface requires that the clock rate to the card is adjusted while

the CPU in the card is running code so that the baud rate can be changed or the performance

of the card can be increased. The protocols that govern the negotiation of these clock rates and

the altering of the clock rate are detailed in ISO7816-3 standard.

The clock is used as the CPU clock for the Smart Card, therefore updates to the microcontroller

clock rate must be synchronized to the SmartCard clock, i.e. the clock high or low pulse widths

must not be shorter than either the old or new programmed value.

AN2284 Datasheet(PDF) 11 Page - STMicroelectronics