Electronic – Smart Card Reader IC interface

smart-card

I am trying to implement Smart Card Reader( MFRC523 Reader) using Controller LPC2138 interface.

Link for datasheet:
http://www.nxp.com/documents/data_sheet/MFRC523.pdf

I have interfaced MFRC523 smart card reader to LPC2138 using I2C protocol. For I2C interface, IC datasheet suggests NRSTPD pin to controller interface.

But due to shortage of I/O pin ( all I/Os used for other application ), I have hardwired NRSTPD pin to Logic High state.

As per datasheet,

NRSTPD ( Input ): ( reset and power-down input )
reset: enabled by a positive edge
power-down: enabled when LOW; internal current sinks are switched off, the oscillator
is inhibited and the input pins are disconnected from the outside world

So Can I hardwired NRSTPD pin to Logic High.

Please guide and thanks in advance.

Best Answer

It looks like the reset functionality of that pin is enabled by the positive edge of a pulse and the power down is enabled by pulling it LOW, so if you have the pin tied to HIGH, there won't be positive edge of a pulse to reset the chip, during normal operation, and power down won't happen cause it isn't low.