TH71221 datasheet(20/44 Pages) MELEXIS

20 / 44 page

TH71221

27 to 930MHz

FSK/FM/ASK Transceiver

39010 071221

Page 20 of 44

Data Sheet

Rev. 005

June/07

Due to the static CMOS design, the SCI consumes virtually no current and it can be programmed in active as

well as in standby mode.

If the transceiver is set from standby mode to any of the active modes (idle, receive, transmit), the SCI set-

tings remain the same as previously set in one of the active modes, unless new settings are done on the SCI

while entering into an active mode.

Fig. 13: Serial Data Input Timing

As shown in the previous section there are four control words which stipulate the operation of the whole chip.

In Stand-alone User Mode SUM the intrinsic default values with respect to the applied levels at pins FS0 and

FS1 lay down the configuration of the transceiver. In Programmable User Mode (PUM) the register settings

can be changed via 3-wire interface SCI. The default settings which vary with the desired operating

frequency depend on the voltage levels at the frequency selection pins FS0 and FS1 before entering the

PUM. Table 5.1.1 shows the default register settings of different frequency selections. It should be noted that

the channel frequency listed below will be achieved with a crystal frequency of 7.1505 MHz. The following

table depicts an overview of the register configuration of the TH71221.

tCWL

tCWH

SDEN

SDTA

bit 23

bit 22

bit 1

bit 0

MSB

Invalid

data

Invalid

data

LSB

SCLK

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