MFRC523 Просмотр технического описания (PDF) - NXP Semiconductors.

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MFRC523

Contactless Reader IC

NXP Semiconductors. 

NXP Semiconductors

MFRC523

Contactless reader IC

8.3.4.11 Switching between F/S mode and HS mode

After reset and initialization, the MFRC523 is in Fast mode (which is in effect F/S mode as

Fast mode is downward-compatible with Standard mode). The connected MFRC523

recognizes the “S 00001XXX A” sequence and switches its internal circuitry from the Fast

mode setting to the HS mode setting.

The following actions are taken:

1. Adapt the SDA and SCL input filters according to the spike suppression requirement

in HS mode.

2. Adapt the slope control of the SDA output stages.

It is possible for system configurations that do not have other I2C-bus devices involved in

the communication to switch to HS mode permanently. This is implemented by setting

Status2Reg register’s I2CForceHS bit to logic 1. In permanent HS mode, the master code

is not required to be sent. This is not defined in the specification and must only be used

when no other devices are connected on the bus. In addition, spikes on the I2C-bus lines

must be avoided because of the reduced spike suppression.

8.3.4.12

MFRC523 at lower speed modes

MFRC523 is fully downward-compatible and can be connected to an F/S mode I2C-bus

system. The device stays in F/S mode and communicates at F/S mode speeds because a

master code is not transmitted in this configuration.

MFRC523_33

Product data sheet

PUBLIC

All information provided in this document is subject to legal disclaimers.

Rev. 3.3 — 5 March 2010

115233

© NXP B.V. 2010. All rights reserved.

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