 2003 Microchip Technology Inc.

DS40232H-page 21

MCRF450/451/452/455

6.2.2

STRUCTURE OF DEVICE

RESPONSE

When the device receives the Interrogator command, it

responds with 70 kHz Manchester encoded data

having the following structures:

Device Response to FRR Command: Preamble (8

bits) + TC (3 bits) + TP (4 bits) + ‘0’ + 32 bits of Tag ID

(Block 1 data) + FRF data (32 - 96 bits) + Calculated

CRC (SCRC, 16 bits) of Tag ID and FRF data = 96 - 160

bits depending on FRF data length.

Note: The preamble + TC + TP + ‘0’ are not included

for the CRC calculation.

Device Response to FRB Command: Preamble (8

bits) + ‘00001’ + ‘000’ + 32 bits of Tag ID (Block 1 data)

+ Stored CRC (SCRC, 16 bits) of Block 1 = 64 bits.

Device Response of Interrogator’s Read command

for Blocks 0 and 2:

Preamble (8 bits) + Block Number (5 bits) + ‘000’ +

Block Data (32 bits) + Calculated 16 bit CRC (CCRC).

Note: The CCRC is calculated by using block number

and block data only. Preamble and ‘000’ are not

included in the CRC calculation.

Device Response of Interrogator’s Read Command

for all other blocks:

Device Response = Preamble (8 bits) + Block Number

(5 bits) + ‘000’ + Block Data (32 bits) + Stored CRC

(SCRC, 16 bits) in the same block.

TABLE 6-3:

INTERROGATOR COMMANDS AND DEVICE RESPONSES

Interrogator Command

Delay

Device Response

Read Block 0 and Block 2

data

Preamble, block #, ‘000’, block data, CCRC

Read block data except for

Block 0 and Block 2

Preamble, block #, ‘000’, block data, SCRC

Write block data

For Blocks 0 and 2: Preamble, block #, ‘000’, block data, CCRC

For all others: Preamble, block #, ‘000’, block data, SCRC

Set Fast Read (FR) bit

T

WRITE

Preamble, 1 byte ‘0’s, Block 0 data, CCRC

Clear Fast Read (FR) bit

T

WRITE

Preamble, 1 byte ‘0’s, Block 0 data, CCRC

Set Talk First (TF) bit

T

WRITE

Preamble, 1 byte ‘0’s, Block 0 data, CCRC

Clear Talk First (TF) bit

T

WRITE

Preamble, 1 byte ‘0’s, Block 0 data, CCRC

End Process (EP)

Preamble

FRR

f(TSMAX, TCMAX, 8-bit Tag ID) Preamble,TC, TP, ‘0’, Tag ID, FRF, FRR_CCRC

FRB

T

DECODE

Preamble, address of block #1 (‘00001’), ‘000’, Tag ID (32 bits),

SCRC of Block 1

References used in this table are as follows:

Preamble = 11111110 (8 bits).‘0’ is transmitted last.

Block # = 5 bit addressed block, transmits Least Significant bit (LSb) first.

Block data = 32-bit data of the addressed block, transmits LSb first.

CCRC = Calculated CRC of the preceding block number and block data. Transmits LSb first.

SCRC = Stored CRC. This SCRC is the CRC of the Write command, address, and data from the Interrogator, LSb first. The device

stores the received CRC for each block. See Section 7.2 “Stored CRC (SCRC) Memory Section” for details.

FRR_CRC = Calculated CRC of 32-bit Tag ID and fast read field (FRF) data.

TP = Tag parameters (4 bits: ‘0’, DF0, DF1, parity). where DF0 and DF1 determine the FR field length (see Table 7-6).

TC = Transmission counter (3 bits), transmits LSb first.

Parity = Even parity bit of TC and TP.

Tag ID = 32 bits of unique identification code of the device, transmits LSb first. This Tag ID is preprogrammed in the factory prior to

shipping.

8-bit Tag ID = 8 bits of Tag ID selected from the 32 bits of the unique tag identification code. Transmits LSb first (see Section 6.2.3.6

“Calculation Of Matching Code” for selecting the 8 bits from the Tag ID).

FRF = Fast Read Field (Blocks 3-5), transmits LSb first (see Section 7.0 “Memory Section”).

f(TSMAX, TCMAX, 8-bit Tag ID = Delay is a function of the TSMAX, TCMAX and 8-bit Tag ID.

T

T

Examples are given in Section 9.0 “Examples”.