MFRC522 datasheet(37/109 Pages) NXP

37 / 109 page

112132

Product data sheet

Rev. 3.2 — 22 May 2007

37 of 109

NXP Semiconductors

MFRC522

Contactless Reader IC

9.2.3.10

TMode Register, TPrescaler Register

Defines settings for the timer.

Remark: The Prescaler value is split over two registers.

Table 91:

TModeReg register (address 2Ah); reset value: 00h

Bit

Symbol

TAuto

TGated

TAutoRestart

TPrescaler_Hi

Access

Rights

r/w

Table 92:

Description of TModeReg bits

Bit

Symbol

Description

TAuto

Set to logic 1, the timer starts automatically at the end of the

transmission in all communication modes at all speeds. The timer stops

immediately after receiving the first data bit if the bit RxMultiple in the

If RxMultiple is set to logic 1, the timer never stops. In this case the

timer can be stopped by setting the bit TStopNow in register ControlReg

to logic 1.

Set to logic 0 indicates, that the timer is not influenced by the protocol.

6 to 5

TGated

The internal timer is running in gated mode.

Remark: In the gated mode, the bit TRunning is logic 1 when the timer

is enabled by the register bits. This bit does not influence the

gating signal.

Value

Description

Non gated mode

Gated by MFIN

Gated by AUX1

Gated by A3

TAutoRestart

Set to logic 1, the timer automatically restart its count-down from

TReloadValue, instead of counting down to zero.

Set to logic 0 the timer decrements to 0 and the bit TimerIRq is set to

logic 1.

3 to 0

TPrescaler_Hi Defines higher 4 bits for TPrescaler.

The following formula is used to calculate fTimer:

fTimer = 6.78 MHz/TPreScaler.

For detailed description see Section 13 “Timer Unit”.

Table 93:

TPrescalerReg register (address 2Bh); reset value: 00h

Bit

Symbol

TPrescaler_Hi

Access

Rights

r/w

Table 94:

Description of TPrescalerReg bits

Bit

Symbol

Description

7 to 0

TPrescaler_Lo Defines lower 8 bits for TPrescaler.

The following formula is used to calculate fTimer:

fTimer = 6.78 MHz/TPreScaler.

For detailed description see Section 13 “Timer Unit”.

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