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TRF7962A: RF Field down after tx/rx cycle - Code Status Control reset from 0x21 to 0x8F

6232381
Prodigy 20 points
Part Number: TRF7962A

Hey,

I am currently implementing a firmware for a device using the TRF7962A. It should support the SLIX2 Privacy mode. Especially getting them out of it again

with a "GET-RANDOM" and a "SET-PASSWORD command without shutting of the rf field.

Before a command I set my Code Status Control to 0x21 / 0b00100001 to enable the rf field. After TX the command and RX the result the Code Status Control (when reading it directly from the TRF7962A) changed to  0x8F / 0b10001111 resulting in a disabled rf field.

This means I am unable to revive chips from privacy mode. Is there anything I have missed to keep the rf field on even after a command?

PS: With a proxmark3 as simulated tag it works fine, as it ignores if the rf field goes down. So the code for get-random/set-password is fine.

  • 0
    TI__Mastermind 18265 points

    Hello,

    I wonder where the value 0x8F in the Chip Status Control register comes from. There is not automatic setting of this register.

    Are you using one of TIs firmware examples or do you have written own firmware? Please check if there is an access to this register which changes the TX on bit.

    That TX is still on after a command has to work because this is necessary i.e. for the implementation of the ISO15693 Inventory command.

    Best regards,

    Helfried

  • 0 in reply to Helfried Vollbrecht
    Prodigy 20 points

    I more or less copied the sample firmware code. 

    The problem were indeed RESET_FIFO commands.

    I removed the RESET_FIFO from TX_COMPLETE and RX_COMPLETE within the irq handler and that problem was solved.