XRA00 datasheet(28/40 Pages) STMICROELECTRONICS

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XRA00

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PingID

The PingID command is a Basic command that

gives rise to a response from the XRA00.

When the command is sent, the XRA00 will re-

spond if the data sent by the Reader in the [VAL-

UE] field matches the data in the XRA00's internal

memory starting at the location specified by the

[PTR] field. Data in the [VALUE] field is compared

to the XRA00 memory, from the lowest to the high-

est memory address. XRA00 devices whose data

matches all of the bits in the [VALUE] field will re-

ply to the Reader. XRA00 devices whose data

does not match or that fail a parity test on any of

the parity bits will not modulate.

The PingID command is used as part of a multi-

XRA00 anti-collision algorithm described in detail

hereafter.

XRA00 devices that match the data sent by the

Reader respond with 8 address bits, from a point

designated by two parameters supplied by the

Reader, in increasing address order.

Each XRA00 response is placed in one of 8 Bin

Response Windows delineated by BIN pulses sent

by the Reader.

Example of a PingID Command. A Reader is-

sues a PingID command containing the following

data:

[CMD] =

00001000b

(PingID)

[PTR] =

00000111b

(0x07)

[LEN] =

00001001b

(0x09)

[VALUE] = 000101101b

(0x2D)

The XRA00 devices will attempt to check 9 bits of

their address data, starting at bit 7 against the data

specified in the [VALUE] field.

In the example shown in Table 10., the underlined

bits in the XRA00 ID code are compared with the

[VALUE] data sent by the Reader. Bits shown in

Italic are modulated and returned to the Reader

during one of the Bin Response Windows. The

lowest 3 bits of the response determine the re-

sponse bin number.

Table 10. Example of PingID Operation

Figure 30. PingID Answer Frame Structure for XRA00 3

PingID Answer Frame

The PingID command is used in the anti-collision

algorithm. This command requires that the XRA00

devices that match the data sent by the Reader re-

ply with 8 modulated data bits in one of 8 Bin Re-

XRA00 ID Code/Bit Position

XRA00 responds to

PingID command

Bin for

response

8-Bit

response

Towards Highest

Address Bit

Lowest Address Bit

MSB

LSB

Bit Number

...321098765432109876543210

XRA00 1 ID

...

010001000001011011101010b

YES

Bin 4 (100b)

01000100b

XRA00 2 ID

...1001111000010

01010010010b

(bit 10 does not match)

XRA00 3 ID

...

111101010001011011110110b

YES

Bin 5 (101b)

11110101b

XRA00 4 ID

...

101100000001011011110111b

YES

Bin 0 (000b)

10110000b

Bin 5

(101)

Bin 6

(110)

10101111 (pattern reflects order of transmission)

Tag Data (8 bits)

Lowest XRA00

address

Highest XRA00

address

ai10769

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