Clock signal switching device of an IC Card

Details Clock signal switching device of an IC Card Clock signal switching device of an IC Card

1989-04-07

1990-11-06

James, Andrew J.

Electrical transmission or interconnection systems

Nonlinear reactor systems

Parametrons

307 64, 307 65, 3072966, 377 15, 377 19, 377 32, H03K 513, H03K 301

Patent

active

049688995

ABSTRACT:
When an IC card is attached to a terminal unit, a counter counts pulses of an external clock signal and a switching circuit outputs the external clock signal to an internal circuit in place of an internal clock signal if a NAND gate determines that the count of pulses of the external clock signal by the counter is a predetermined value. When the IC card is ejected from the terminal unit, pulses of the internal clock signal are counted by a counter and when the count attains a predetermined value, the counter is cleared and the switching circuit outputs the internal clock signal to the internal circuit in place of the external clock signal in response to the output of the NAND gate. Thus, it can be correctly determined whether the IC card is operated in the form of a single body or in the form attached to any terminal unit.

REFERENCES:
patent: 4612657 (1986-09-01), Takahashi
patent: 4651072 (1987-03-01), Takata
patent: 4675539 (1987-06-01), Nichol
patent: 4850000 (1989-07-01), Dias

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