mfrc531 NXP Semiconductors, mfrc531 Datasheet - Page 18

• Manufacturer Part Number: mfrc531
• Description: Iso/iec 14443 Reader Ic
• Manufacturer: NXP Semiconductors

NXP Semiconductors
MFRC531_34
Product data sheet
PUBLIC
9.3.2 Controlling the FIFO buffer
9.3.3 FIFO buffer status information
Table 17.
In addition to writing to and reading from the FIFO buffer, the FIFO buffer pointers can be
reset using the FlushFIFO bit. This changes the FIFOLength[6:0] value to zero, bit
FIFOOvfl is cleared and the stored bytes are no longer accessible. This enables the FIFO
buffer to be written with another 64 bytes of data.
The microprocessor can get the following FIFO buffer status data:
Remark: Setting the FlushFIFO bit clears the FIFOOvfl bit.
The MFRC531 can generate an interrupt signal when:
The HiAlert flag bit is set to logic 1 only when the WaterLevel[5:0] bits or less can be
stored in the FIFO buffer. The trigger is generated by
The LoAlert flag bit is set to logic 1 when the FIFOLevel register’s WaterLevel[5:0] bits or
less are stored in the FIFO buffer. The trigger is generated by
HiAlert
LoAlert
Active
command
ReadE2
LoadKeyE2
LoadKey
Authent1
Authent2
LoadConfig
CalcCRC
•
•
•
•
•
•
the number of bytes stored in the FIFO buffer: bits FIFOLength[6:0]
the FIFO buffer full warning: bit HiAlert
the FIFO buffer empty warning: bit LoAlert
the FIFO buffer overflow warning: bit FIFOOvfl.
bit LoAlertIRq is set to logic 1 and bit LoAlert = logic 1, pin IRQ is activated.
bit HiAlertIRq is set to logic 1 and bit HiAlert = logic 1, pin IRQ activated.
=
=
FIFO buffer access
(
FIFOLength
64 FIFOLength
–
FIFO buffer
μp Write
yes
yes
yes
yes
-
yes
yes
Rev. 3.4 — 26 January 2010
≤
WaterLevel
μp Read
yes
-
-
-
-
-
-
…continued
)
056634
≤
WaterLevel
Remark
the microprocessor has to prepare the arguments,
afterwards only reading is allowed
Equation
Equation
1:
ISO/IEC 14443 reader IC
MFRC531
© NXP B.V. 2010. All rights reserved.
2:
18 of 116
(1)
(2)