XRA00 datasheet(7/40 Pages) STMICROELECTRONICS

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XRA00

Symbol Transmission Format for Request

Frame

Modulation of negative pulse width (RF interrup-

tion period) is used for data transmission and syn-

chronization

XRA00s.

Four

timings

are

distinguished by their shortness. Their symbols

are as follows:

■

tfwhm0: encode binary data "0"

■

tfwhm1: encode binary data “1”

■

tfwhmBin: encode Bin synchroniZation pulse

■

ttrangap: encode Transaction Gap pulse

Each symbol is referenced to the Master Clock

Time Period, t0, which is defined by the Reader

during the Request Frame header modulation. t0 is

the bit duration period generated by the Reader.

Request Binary Data "0"

Data Modulation Timing, tfwhm0, for Reader-to-

XRA00 clocking when data = "0", is encoded by a

"narrow" 1/8t0 pulse width modulation. This timing

is also used during data synchronization at the be-

gining of each Request Frame. tfwhm0 is illustrated

in Figure 6.

Request Binary Data "1"

Data Modulation Timing, tfwhm1, for Reader-to-

XRA00 clocking when data = "1", is encoded by a

"wide" 3/8t0 pulse width modulation. This timing is

also used for SOF (Start Of Frame) and EOF (End

Of Frame) symbols within the Request Frame.

tfwhm1 is illustrated in Figure 7.

Bin pulse and Bin Response Window

XRA00 Answer Frames are synchronized by the

Reader using Bin pulse modulation. The Bin pulse

is encoded by a 3/8t0 pulse width modulation.The

Bin pulse is also used to define the Bin Response

Window time slots during the inventory sequence

after a PINGID command is issued. The Bin Re-

sponse Window is shown in Figure 8.

Transaction Gap

During communication with XRA00, each Request

Frame begins with a transaction gap, ttrangap, fol-

lowed by a period of time, ttransetup, during which

the carrier frequency is unmodulated (See Figure

9. for an illustration and Table 2. for the value of

ttransetup). ttransetup precedes the Data Modulation

Window.

Power Up

If during communication with the Reader the carri-

er is turned off for a time exceeding tReset , XRA00

loses DC power. After XRA00 is powered up

again, a minimum time of ttransetup, during which

the carrier frequency is unmodulated, must pre-

cede the Data Modulation Window. (See Figure

10. for an illustration and Table 2. for the value of

ttransetup.)

Figure 6. Data Modulation Timing - “0”

Figure 7. Data Modulation Timing - “1”

Clock Low

(Data '0')

ai10745

'0'

fwhm0

= 1/8t

Clock Low

(Data '1')

ai10746

'1'

fwhm1

= 3/8t

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