T5743 Ver la hoja de datos (PDF) - Atmel Corporation

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T5743

UHF ASK/FSK Receiver

Atmel Corporation 

Sleep Mode

T5743

ISpoll = I--S----o--f--f--´-----T---T-S---Sl-e--l-ee---ep--p--+--+---I--ST---o-S--n-t--a-´-r--t-u(---Tp----S+---t-a-T--r--tB-u--i-pt----c-+-h---e-T--c--Bk---i-t----c--h---e---c--k---)

During TSleep and TStartup the receiver is not sensitive to a transmitter signal. To guaran-

tee the reception of a transmitted command the transmitter must start the telegram with

an adequate preburst. The required length of the preburst depends on the polling

parameters TSleep, TStartup, TBit-check and the start-up time of a connected microcontroller

(TStart,µC). Thus, TBit-check depends on the actual bit rate and the number of bits (NBit-check)

to be tested.

The following formula indicates how to calculate the preburst length.

TPreburst ³ TSleep + TStartup + TBit-check + TStart_µC

The length of period TSleep is defined by the 5-bit word Sleep of the OPMODE register,

the extension factor XSleep (according to Table 9), and the basic clock cycle TClk. It is

calculated to be:

TSleep = Sleep ´ XSleep ´ 1024 ´ TClk

In US- and European applications, the maximum value of TSleep is about 60 ms if XSleep

is set to 1. The time resolution is about 2 ms in that case. The sleep time can be

extended to almost half a second by setting XSleep to 8. XSleep can be set to 8 by bit

XSleepStd to 1.

According to Table 8, the highest register value of sleep sets the receiver into a perma-

nent sleep condition. The receiver remains in that condition until another value for Sleep

is programmed into the OPMODE register. This function is desirable where several

devices share a single data line and may also be used for microcontroller polling — via

Pin POLLING/_ON, the receiver can be switched on and off.

11

4569A–RKE–12/02

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