SPI_FLASH_FAST_READ_DUAL_IO and Winbond W25Q32JV.

[at91rm9200]

Hello Bruno,

I have the Winbond W25Q32JV FLASH now working in SPI_FLASH_FAST_READ_DUAL_IO mode. According to the data sheet, this FLASH does not need dummy cycles in Fast Read Dual I/O mode. Instead of 8 dummy cycles (two byte) it needs one single Mode byte, correspondent to 4 cycles. The mode bits 5 and 4 should not equal to 2'b10, since this would change the behavior of the next read command.

From MappedSPIFlash.v, line 295:

clock_cnt <= 5'd28; // cmd: 8 clocks address: 12 clocks dummy: 8 clocks

If I set clock_cnt to 5'd24, everything is fine with my board. I tested with 16 MHz and 66 MHz clock frequency.

Regards, Bernd.

[BrunoLevy]

Hi Bernd,

• Thank you very much for the feedback. I just received an IceBreaker with a Winbond W25Q128JV-DTR, that seems to be similar. I'll add some options to configure the number of dummy clocks. With this chips we can go even faster (>4x) by
  • using QuadIO mode (if all the pins are wired to the FPGA, which is not the case on the IceStick for instance)
  • using DTR mode
  • using XIP mode (no longer need to send command, just send address and read data) I'll do some tests...

[at91rm9200]

Thank you.