MFRC522 datasheet(43/96 Pages) NXP

43 / 96 page

MFRC522_33

Product data sheet

PUBLIC

Rev. 3 — 26 October 2009

112133

43 of 96

NXP Semiconductors

MFRC522

Contactless reader IC

9.3.1.13

ControlReg register

Miscellaneous control bits.

Table 44.

WaterLevelReg register bit descriptions

Bit

Symbol

Description

7 to 6

reserved

reserved for future use

5 to 0

WaterLevel

[5:0]

deﬁnes a warning level to indicate a FIFO buffer overﬂow or underﬂow:

Status1Reg register’s HiAlert bit is set to logic 1 if the remaining

number of bytes in the FIFO buffer space is equal to, or less than the

deﬁned number of WaterLevel bytes

Status1Reg register’s LoAlert bit is set to logic 1 if equal to, or less

than the WaterLevel bytes in the FIFO buffer

Remark: to calculate values for HiAlert and LoAlert see

Section 9.3.1.8 on page 40.

Table 45.

ControlReg register (address 0Ch); reset value: 10h bit allocation

Bit

Symbol

TStopNow TStartNow

reserved

RxLastBits[2:0]

Access

Table 46.

ControlReg register bit descriptions

Bit

Symbol

Value Description

TStopNow

timer stops immediately

reading this bit always returns it to 0

TStartNow

timer starts immediately

reading this bit always returns it to 0

5 to 3

reserved

reserved for future use

2 to 0

RxLastBits[2:0]

indicates the number of valid bits in the last received byte

if this value is zero, the whole byte is valid

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