mfrc522 NXP Semiconductors, mfrc522 Datasheet - Page 68

• Manufacturer Part Number: mfrc522
• Description: Contactless Reader Ic
• Manufacturer: NXP Semiconductors

NXP Semiconductors
14. Interrupt Request System
112132
Product data sheet
The MFRC522 indicates certain events by setting bit IRq in the register Status1Reg and
additionally, if activated, by pin IRQ. The signal on pin IRQ may be used to interrupt the
host using its interrupt handling capabilities. This allows the implementation of efficient
host software.
The following table shows the available interrupt bits, the corresponding source and the
condition for its activation. The interrupt bit TimerIRq in register CommIRqReg indicates
an interrupt set by the timer unit. The setting is done when the timer decrements from 1
down to 0.
The TxIRq bit in register CommIRqReg indicates that the transmitter has finished. If the
state changes from sending data to transmitting the end of the frame pattern, the
transmitter unit sets the interrupt bit automatically. The CRC coprocessor sets the bit
CRCIRq in the register DivIRqReg after having processed all data from the FIFO buffer.
This is indicated by the bit CRCReady = 1.
The bit RxIRq in register CommIRqReg indicates an interrupt when the end of the
received data is detected.
The bit IdleIRq in register CommIRqReg is set if a command finishes and the content of
the command register changes to idle.
The bit HiAlertIRq in register CommIRqReg is set to logic 1 if the HiAlert bit is set to
logic 1, that means the FIFO buffer has reached the level indicated by the bit WaterLevel.
The bit LoAlertIRq in register CommIRqReg is set to logic 1 if the LoAlert bit is set to
logic 1, that means the FIFO buffer has reached the level indicated by the bit WaterLevel.
The bit ErrIRq in register CommIRqReg indicates an error detected by the contactless
UART during sending or receiving. This is indicated by any bit set to logic 1 in register
ErrorReg.
Table 148: Interrupt Sources
Interrupt bit
TimerIRq
TxIRq
CRCIRq
RxIRq
IdleIRq
HiAlertIRq
LoAlertIRq
ErrIRq
Interrupt Source
Timer Unit
Transmitter
CRC co-processor
Receiver
Command Register
FIFO-buffer
FIFO-buffer
contactless UART
Rev. 3.2 — 22 May 2007
Is set automatically, when
the timer counts from 1 to 0
a transmitted data stream ends
all data from the FIFO buffer has been processed
a received data stream ends
a command execution finishes
the FIFO-buffer is getting full
the FIFO-buffer is getting empty
an error is detected
Contactless Reader IC
MFRC522
© NXP B.V. 2007. All rights reserved.
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