26
Analog Front End IC TMS37122 - Reference Guide August ’01
currence of WAKEI for maximum 17 EOBI pulses. At each negative transition of EOBI a 7-
bit counter is reset and starts to count the regenerated RF clock (CLKI). If the counter reaches
the Pulse Position Modulation (PPM) threshold before the next negative transition, the
counter is stopped and a high bit is shifted in a compare shift register with this transition. The
PPM threshold is defined by the Configuration Memory and can be selected depending on the
desired data rate. In the other case the negative transition occurs before the threshold is
reached and a low bit is shifted.
Bit-by-bit the received pattern is compared with the two Wake-Pattern (Passive Entry, Pas-
sive Start) loaded from Configuration Memory during Standby-Mode and result is reported
to the Control Unit.
2.8 Control Unit
The Control Unit of the TMS37122 is supplied by the battery voltage (VBAT) and controls
the complete device. Therefore also VCL supplied parts are only usable in case of sufficient
VBAT supply voltage. The Control Unit has three main states called Off-Mode, Standby-
Mode, Transparent-Mode and LF Transmission Mode and several intermediate states (see
Figure 13). Interactions between the states are explained below in detail with extracted Fig-
ures.
To Next Page
Loading...
Need help?
General
