mfrc531 NXP Semiconductors, mfrc531 Datasheet - Page 76

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

NXP Semiconductors
MFRC531_34
Product data sheet
PUBLIC
11.2.1.1 Using the Transmit command
11.2.1 Transmit command 1Ah
11.2 Commands for ISO/IEC 14443 A card communication
The MFRC531 is a fully ISO/IEC 14443 A and ISO/IEC 14443 B compliant reader IC. This
enables the command set to be more flexible and generalized when compared to
dedicated MIFARE reader ICs.
set for ISO/IEC 14443 A card communication and related communication protocols.
Table 132. Transmit command 1Ah
The Transmit command reads data from the FIFO buffer and sends it to the transmitter. It
does not return any data. The Transmit command can only be started by the
microprocessor.
To transmit data, one of the following sequences can be used:
When the transmitter requests the next data byte to ensure the data stream on the RF
interface is continuous and the FIFO buffer is empty, the Transmit command automatically
terminates. This causes the internal state machine to change its state from transmit to
idle.
When the data transmission to the card is finished, the TxIRq flag is set by the MFRC531
to indicate to the microprocessor transmission is complete.
Remark: If the microprocessor overwrites the transmit code in the Command register
with another command, transmission stops immediately on the next clock cycle. This can
produce output signals that are not in accordance with ISO/IEC 14443 A.
Command
Transmit
1. All data to be transmitted to the card is written to the FIFO buffer while the Idle
2. The command code for the Transmit command is stored in the Command register.
3. Part of the data transmitted to the card is written to the FIFO buffer while the Idle
command is active. Then the command code for the Transmit command is written to
the Command register.
Remark: This is possible for transmission of a data stream up to 64 bytes.
Since there is not any data available in the FIFO buffer, the command is only enabled
but transmission is not activated. Data transmission starts when the first data byte is
written to the FIFO buffer. To generate a continuous data stream on the RF interface,
the microprocessor must write the subsequent data bytes into the FIFO buffer in time.
Remark: This allows transmission of any data stream length but it requires data to be
written to the FIFO buffer in time.
command is active. Then the command code for the Transmit command is written to
the Command register. While the Transmit command is active, the microprocessor
can send further data to the FIFO buffer. This is then appended by the transmitter to
the transmitted data stream.
Remark: This allows transmission of any data stream length but it requires data to be
written to the FIFO buffer in time.
Value
1Ah
Rev. 3.4 — 26 January 2010
Action
transmits data from FIFO buffer to card
056634
Section 11.2.1
to
Section 11.2.5
Arguments
and data
data stream
describe the command
ISO/IEC 14443 reader IC
MFRC531
© NXP B.V. 2010. All rights reserved.
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data
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