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trf7970a fifo status always 0x00

Rutger 123
Prodigy 20 points

Hello,

I have a problem with the fifo status register (0x1C), the register always contains 0x00.
I try to send a REQB sequence and using this data

8Fh (cmd:Reset)
91h (cmd:Transmission with CRC)
3Dh (ads:1Dh ,continuous mode)
00h,30h (set length=3 to registers:1D&1E)
05h,00h,00h (set REQB format to register-1F)

After writing to trf7970

IRQ 1
0x80 (irqTX)
8Fh (cmd:Reset)

IRQ 2
0x40 (irqRX)
Read FIFO Status register (0x1C)

The fifo status register always contains 0x00
Is there any reason this stays at 0x00 ? am i doing something wrong?

Tnx,
Rutger

  • 0
    TI__Guru* 91206 points

    Rutger - 

    did you set up the ISO control register to 0x0C beforehand and turn on the transmitter (via 0x00 register)? 

    See here below doing so via continuous register write. 

    then sending out the command, as you have listed

    Servicing the interrupt for EOTX

    Getting the EORX IRQ, servicing and then retrieving ATQB

  • 0 in reply to Josh Wyatt
    Prodigy 20 points

    Josh,

    Thank you very much.
    I did set the ISO control register to 0x0C but i noticed some register values were different then the ones you are writing in you continuous register write.
    I started to compare your register values with mine and found my mistake.

    In the Modulator and SYS_CLK control register i noticed i was using the default value which has the 27MHZ bit set.
    After clearing this bit i got it working.

    Thank you,
    Rutger