MK64 : How to change the Flexbus hold timing

[koichisakagami]

Dear community,

I consider the Flexbus read timing .

In figure 13. FlexBus read timing diagram of K64P144M120SF5 rev6,About Flexbus timing,
  the time from CLK_RISE to FB_OE (control signals) is covered by the FB3 spec,
  the time from CLK_RISE to input Date hold time spec is FB5.

      FB3 is 0 ns (Min).
      FB5 is 0.5 ns  (Min).

I connect the flash memory to Flexbus.
The flash memory AC timing is as follows.
    OE# to output transition is 0 ns (Min).

In the case of without including board delay, the Hold time is not enough for MCU read timing.

[Question]
Is it possible to ensure the hold time by setting a register (Chip Select Control Register ...) ?
I hope to use in "AA = 1" (Auto-Acknowledge Enable ) setting .

    Best Regards,
     Koichi Sakagami

[xiangjun_rong]

Hi, Koichi,

Can you tell us the part number of the flash you are using?  If you want to use in "AA = 1" (Auto-Acknowledge Enable ) setting, you have to use FPGA/CPLD or the similar programmable device to generate the FB_TA signal, as you know the FB_TA pin is an input pin. I do not suggest you use the mode with Auto-Acknowledge Enabled, I suggest you use the mode with Auto-Acknowledge disabled. If you use the low speed flash device, you can enlarge the reading/writing timing by programming the FlexBus registers.

Regarding your question "The flash memory AC timing is as follows.     OE# to output transition is 0 ns (Min). In the case of without including board delay, the Hold time is not enough for MCU read timing.", of course, this is your flash it's own characteristic,programming the FlexBus module is useless. Regarding the FB5, it is 0.5nS at least, it means that the the data from memory is latched into K64 core register with the rising edge of FB_CLK, we can guarantee that the FB_OE will rise after the the holding time with FB5 which is at least 0.5ns. So it is okay for your flash with the time which OE# to output transition is 0 ns (Min).

In conclusion, it is okay to hook the flash with FlexBus and use the mode with Auto-Acknowledge disabled.

Hope it can help you.

BR

XiangJun Rong