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Forum Post: RE: Cannot get the TMS3705 to enter synchronous data transfer mode

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Hello John...

At risk of being labelled a serial pest on this forum I still have hope.

While I cannot help with your immediate problem, perhaps you can share your knowledge about "transponder frequency matching"

I see you are using the TMS3705A in the "Automatically adjusting the carrier frequency to the transponder resonant frequency" mode.
ie MCR = 0111100

First, have you sighted document "1030.LF TMS3705A ASIC.pdf "...

I point you consider two note mentions here.

page 24, " For correct writing to MCR, it is essential to know if the IC is in IDLE or SLEEP mode ?

page 27, State Diagram Notes...Note 4: "...Only default mode is fully supported when starting an operation from SLEEP with only one falling edge on TXCT ..."

As Asynchronous Mode is a "Default mode (bits 6)"; as is Division Factor 119 (bits 1-4) "A default mode" and you cannot break out of these conditions. something is stopping you from writing to the MCR (obviously).

My thoughts are these


1. on a first of two passes, wake up the chip with a 50uS "Twake"...then do your write to MCR on next attempt...?
2. try MCR = 0011000, out of curiosity then wake it up ... page 27 may be your spark  to retry, me on thin ice here.

So now, when you have your system working in the (unwanted) Asynchronous Mode, could you comment on how well or otherwise this matching to the transponder performs?.

I have curiosity concerning multiple tags (each on different frequencies) in the same detection volume...what happens?

Also, if the Reader Coil is improperly dampened and its resonance Significiently lingers into the 1.6-1.7mS sampling period....what happens?

As the new "adapted charge field frequency" is a good thing, the resonance frequency of the Reader does not also change...

Can you report any spetacular improvement when you use this Frequency matching feature?

Kind Regards
Ray


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