Change SPI clock polarity between a WRITE and a READ instruction

Hello,

I want to access the TI TRF7960 (a 13.56MHz RFID reader/writer) with Espruino running on a nucleo STM32F401RE. The TI chip can be accessed with SPI, but with an exotic trick : clock polarity has to change between a write and a read instruction. Below is a drawing from the application report "Using the SPI Interface With TRF7960" (http://www.ti.com/lit/an/sloa140a/sloa140a.pdf).

How could I do that ? I tried the following but it doesn't work.

var spi = new SPI();
spi.setup({sck:B6, miso:A6, mosi:A7, mode:integer=0, order:'msb'});

digitalWrite(SS, 0);
spi.write(0b01000100);
spi.setup({sck:B6, miso:A6, mosi:A7, mode:integer=3, order:'msb'});
d = spi.write(0b01000100);

digitalWrite(SS, 1);

Thank you :)

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