TH71221_15 Datasheet, PDF (20/44 Pages) Melexis Microelectronic Systems – FSK/FM/ASK Transceiver

TH71221
27 to 930MHz
FSK/FM/ASK Transceiver
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.
Invalid
data MSB
SDTA
bit 23
bit 22
Invalid
LSB
data
bit 1
bit 0
SCLK
t _CS
SDEN
t _CH
t_CWL t_CWH
t_ES
t_EW t_EH
Fig. 13: Serial Data Input Timing
5 Register Description
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.
39010 071221
Rev. 009
Page 20 of 44
Data Sheet
Nov/15