Forum Post: RE: TRF7970A SPI Operation Issue, not responding to reads

Hi Josh,

The MCU is the MK20DX256VLK100 from Freescale. I will more deeply dig into the configuration registers and specs file to confirm about the MOSI line.

Measured values for the times are:

T_HD,SI = 244ns;
T_SU=320ns;
T_LOW=320ns;
T_HI=240ns;
1/f_UCxCLK=560ns (1.786MHz clock speed);

This is a screen shot from the DSO, it shows the first two bits (BIT7,BIT6). Channel 3 is MOSI (first T_SU not shown, but also measured 320ns) and channel 4 is CK.

Victor