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MCRF450

13.56 MHz Read/Write Passive RFID Device

Microchip Technology 

MCRF450/451/452/455

To enhance data integrity for writing, the device

includes an anti-tearing feature. This anti-tearing

feature provides verification of data integrity for

incomplete write cycles due to failed communication

between the Interrogator and the device during the

write sequences.

1.1 Device’s Communication with

Interrogator

The device can be operated in either Fast Read

Request (FRR) or Fast Read Bypass (FRB) mode,

depending on the status of bit 31 (FR: bit) of Block 0. If

the FR bit is set, the device is operated in FRR mode,

and FRB mode, if the FR bit is cleared. The FR bit is

always reprogrammable and not write-protectable. The

FRR mode is a default setting. The communication

between the Interrogator and tag starts with a FRR or

FRB command.

In FRR mode, the device sends a response only when

it receives the FRR command, not the FRB command.

Conversely, the device in FRB mode sends a response

when it receives the FRB command only, not the FRR

command.

If the device is set to FRR mode and also set to TTF

mode (TF bit = set), the device can send the FRR

response as soon as it is energized.

One of the main purposes of using the two different

modes (FRR and FRB) is to use the device effectively

in the item level supply-chain application, where a rapid

identification and an effective anti-collision read/write

process is needed (i.e., to identify whether it is a paid

or unpaid item, or whether it passed one particular point

of interest or not). This can be done by either checking

the status of the FR bit or by checking the response of

the tag to the command. For this reason, the FR bit is

also called an Electronic Article Surveillance (EAS) bit.

1.1.1 OPERATION OF TAG IN FRR MODE

If the device is in the FRR mode (FR bit = set), the

communication between the Interrogator and the

device can start in two ways, depending on the status

of TF (Bit 30 of Block 0). If the TF bit is cleared, it is

called ITF mode. In this case, the tag waits for the

Interrogator’s FRR command and sends the FRR

response data when it sees the FRR command. If the

TF bit is set, the device is in a TTF mode. In this case,

the tag sends the FRR response as soon as it is

energized, even without the FRR command. The tag

has a short listening window (1 ms) immediately after

the FRR response. The Interrogator sends its next

command during this listening window.

The FRR response includes the 32 bits of tag ID and

FRF (Blocks 3 -5). See Tables 7-3, 7-4 and 7-6 for

data. The Interrogator identifies which tags are in the

field by receiving their FRR responses.

Based upon the FRR response, the Interrogator will

send Matching Code 1 (MC1) or Matching Code 2

(MC2) during the tag’s listening window. The Interroga-

tor sends the MC1 to put the tag into Sleep mode. Tags

in Sleep mode never respond to any command.

Removal of the Interrogator’s RF energy from the

device is the only way to wake-up the device.

If the tag needs further read/write processing, the

Interrogator sends the MC2, followed by a Read or

Write command. After the completion of reading or

writing of block data, the Interrogator sends an End

command to put the tag into Sleep mode.

The reading and writing of the FRR devices takes place

in the Anti-collision mode. For instance, if there are

multiple tags in the field, the Interrogator selects one

tag at a time by controlling the tag’s time slot for the

FRR response. The Interrogator repeats this sequence

until all tags in its field are processed:

- send FRR command

- receive FRR response

- send Matching Code 1 or 2 at tag’s listing

window

- send Read Block command/or send Write

Block command and data

- verify read/write response

- send End command

- verify the End command response

- look for other tag’s FRR responses

1.1.2 OPERATION OF TAG IN FRB MODE

The communication with the device in the FRB mode is

initiated by the FRB command only. If the device sees

the Interrogator’s FRB command, it sends its 32-bit tag

ID and waits for the MC2. This is followed by a Read or

Write command. Once the device is read or written, the

Interrogator sends an End command. Unlike the FRR

mode, the reading and writing of the tag are processed

in a non Anti-collision mode.

See Section 6.0 “Read/Write Anti-Collision Logic”,

for the read and write anti-collision algorithm. See

Example 9-1 for command sequences and device

responses.

DS40232H-page 4

 2003 Microchip Technology Inc.

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