how to realize 3-state control,if FPGA are bus master.

[ilikebbs]

xapp246

hi,all
I want to use fpga to read and write flash
fpga are data bus master,how to realize 3-state control?
Could you give me an example?
thanks.

 

[revolt]

hi,

U don't say what language u are using. My example is in VHDL. I hope it helps u.

flashIO<=flash_data when write_en='1' else (others=>'z');

flashIO is an input/output dataport to the flash. When the signal write_en='1' the flash_data appears at the output. during write_en='0' flash_IO is tristate and the flash can put its data on the bus. Reading from the flashIO port is possible all the time.

U have to add your control signal like CS, OE ... etc.

 

[ilikebbs]

I understand.
Do you have example for fpga read and write flash?
thanks

 

[revolt]

Sorry, I don't have a sample for flash devices. U can search examples for aync. SRAM devices they hava a simliar interface.

 

[kib]

check this application note from xilinx
https://www.xilinx.com/bvdocs/appnotes/xapp246.pdf