Passive Entry Wake Pattern; Passive Start Wake Pattern; 10Telegram Duration 'C_Telegr - Texas Instruments TRIS TMS37122 Reference Manual

Tiris automotive devices analog front end ic

Analog Front End IC TMS37122 - Reference Guide

2.10.3.8 Passive Entry Wake Pattern

the clock information (e.g. Manchester Coding). During Transmission Mode (TX=high) the

clock CLKM is available even if CLKA is disabled.

The desired Wake Pattern for the Passive Entry function can be selected as desired. If a sep-

arate transponder for Immobilizer function is in the system, pattern should be avoided, which

are similar to a Challenge telegram. This especially if the Base Station uses same modulation

principle for data transfer to the transponder.

The Wake Pattern for the Passive Start function can be selected as required. If a separate tran-

sponder for Immobilizer function is in the system, patterns which are similar to a Challenge

telegram should be avoided. Especially if the Base Station uses same modulation principle

for data transfer to the transponder.

Attention:

If Passive Start Wake Pattern and Passive Entry Wake Pattern are equal, only

the Passive Start Sensitivity determines if the Transparent Mode is entered.

If the Wake Pattern check detected a non-valid or incomplete Wake Pattern it can be assumed

that a foreign Base Station had requested communication from a foreign Identification De-

vice. To avoid ongoing wake-up of the non-addressed Identification Device a waiting period

is meaningful. Therefore a counter is loaded with ctelegr. The counter counts down using

CLKI as source. The resulting waiting time must be adapted to typical communication dura-

tion after a wake signal (see Table 6). The communication duration consists of the Challenge

Telegram and the UHF Response Telegram, which are together typically in the range of 100

ms. The telegram time is calculated with the following formula:

ttelegr = ctelegr / fTX

August '01

Table of Contents