RC522 datasheet(30/96 Pages) NXP

30 / 96 page

MFRC522_34

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Product data sheet

PUBLIC

Rev. 3.4 — 5 March 2010

112134

30 of 96

NXP Semiconductors

MFRC522

Contactless reader IC

The timer can be started manually using the ControlReg register’s TStartNow bit and

stopped using the ControlReg register’s TStopNow bit.

The timer can also be activated automatically to meet any dedicated protocol

requirements by setting the TModeReg register’s TAuto bit to logic 1.

The delay time of a timer stage is set by the reload value + 1. The total delay time (td) is

calculated using Equation 5:

(5)

An example of calculating total delay time (td) is shown in Equation 6, where the

TPrescaler value = 4095 and TReloadVal = 65535:

(6)

Example: To give a delay time of 25

μs requires 339 clock cycles to be counted and a

TPrescaler value of 169. This configures the timer to count up to 65535 time-slots for

every 25

μs period.

TPrescaler

()

TReloadVal

()

13.56 MHz

---------------------------------------------------------------------------------------------------------

39.59 s

4095

()

65535

()

13.56 MHz

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RC522 Datasheet(PDF) 30 Page - NXP Semiconductors