AFE 5805 Serial Control

Hi,

I'm doing an project on ultrasound. I'm using TI's AFE5805EVM and TSW1250. I have worked with these boards and understood how it works.

Now my aim is to control the AFE5805 chip through my FPGA code serially. In my code what i actually do is send 72 bits of data through SPI lines.

These 72 bits are 0x00, 0x0001,0x42,0x8081,0x46,0x8208.   ie I'm first making a software reset by writing a 0x0001 to address 0x00 to make the registers to its default values and then writing 0x8081 and 0x8208 to address location 0x42 and 0x46 respectively. (This procedure is what i actually do when i use AFE5805 USB SPI.)

In my code i have 3 pins to control AFE. SDATA, SCLK and CSn.  This SDATA pin from my FPGA is directly soldered to ADS_SDATA pin on AFE Board and SCLK to ADS_SCLK and CSn to ADS_CSZ on the board.

Now when i run the code in my FPGA triying to control AFE5805, the chip is not getting initialized. It shows that in my above procedures something is missing so that my chip is not getting initialized. I also tried by initially pressing the Reset button near MSP430 IC on the AFE5805 board and then stream of 72bits was send. That too is not working.

In my code the 72bits is send in a stretch. No delays are given after 24bit delivery. Whether this will create problem???...

Somebody plz help me to get out of this situation....

My simulated wave form is shown below

(please right click on above image and select View Image to get a clear picture)

CLK_IN is 20ns

AFE_SCLK is 50ns

RESET_IN is not for AFE Hardware reset. It is to make the variables in my program to the initial state so that after every reset the above given stream of bits repeats.

Hoping the needful as soon as possible...

THANKS&REGARDS

AR-JITHESH