MFRC522 datasheet(11/96 Pages) NXP

11 / 96 page

MFRC522_33

Product data sheet

PUBLIC

Rev. 3 — 26 October 2009

112133

11 of 96

NXP Semiconductors

MFRC522

Contactless reader IC

8.1.3.2

Selectable UART transfer speeds

The internal UART interface is compatible with an RS232 serial interface.

The default transfer speed is 9.6 kBd. To change the transfer speed, the host controller

must write a value for the new transfer speed to the SerialSpeedReg register. Bits

BR_T0[2:0] and BR_T1[4:0] deﬁne the factors for setting the transfer speed in the

SerialSpeedReg register.

The BR_T0[2:0] and BR_T1[4:0] settings are described in Table 9. Examples of different

transfer speeds and the relevant register settings are given in Table 10.

[1]

The resulting transfer speed error is less than 1.5 % for all described transfer speeds.

The selectable transfer speeds shown in Table 10 are calculated according to the

following equations:

If BR_T0[2:0] = 0:

(1)

If BR_T0[2:0] > 0:

(2)

Remark: Transfer speeds above 1228.8 kBd are not supported.

Table 9.

BR_T0 and BR_T1 settings

BR_Tn

Bit 0

Bit 1

Bit 2

Bit 3

Bit 4

Bit 5

Bit 6

Bit 7

BR_T0 factor

124816

BR_T1 range

1 to 32 33 to 64 33 to 64 33 to 64 33 to 64 33 to 64 33 to 64 33 to 64

Table 10.

Selectable UART transfer speeds

Transfer speed (kBd)

SerialSpeedReg value

Transfer speed accuracy

(%)[1]

Decimal

Hexadecimal

7.2

250

FAh

−0.25

9.6

235

EBh

0.32

14.4

218

DAh

−0.25

19.2

203

CBh

0.32

38.4

171

ABh

0.32

57.6

154

9Ah

−0.25

115.2

122

7Ah

−0.25

128

116

74h

−0.06

230.4

5Ah

−0.25

460.8

3Ah

−0.25

921.6

1Ch

1.45

1228.8

15h

0.32

transfer speed

27.12

BR_T0

()

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

transfer speed

27.12

106

BR_T1

()

BR_T0

–

()

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

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

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