CX3 max fifo delay time issue

[LeoChen]

Hi,

I have got the fifo delay time caculation method from another link, but I'm confused about how to caculate the max fifo delay time. As my understanding, the max fifo delay time = H_total(MIPI CSI-2) - H_active(parallel), but when I compare the caculated value with SDK tool as below picture show, the result is different. As below SDK tool show, max fifo delay time is 6.17us, but not equal to (17.4 - 16.67). So I wonder  if my understanding is right? And is there any other formula to calculate the max fifo delay time?

[AliAsgar]

Hi,

Hactive(MIPI CSI-2) - Hactive(parallel) gives the minimum FIFO delay time.

The maximum FIFO delay time is calculated taking into account internal line buffer. The tool calculates it automatically. 

Best Regards,
AliAsgar

[LeoChen]

Hi AliAsgar,

Could you tell me the length of internal line buffer? And how to calculate the max  fifo delay time, is there a formula?

[AliAsgar · Accepted solution]

Hi,

The length of the internal buffer is 511 bytes.

The formula to calculate the max fifo delay time can be given by 

Fifo Delay time = ((Fifo Delay * 4/Number of Lanes) + 10)/(CSI_Clock/4),

where, Fifo Delay is 511.

Best Regards,
AliAsgar

[LeoChen]

Hi AliAsgar,

The max fifo delay time which calculated by the timing diagram your members shared is different from the tool shows:

As you can see, the tool shows that the max fifo delay time is 6.17us,  but not equal to (17.4 - 16.67) which calculated by the timing diagram your members shared. So is there any other internal line buffer besides the fifo?

[AliAsgar]

Hi,

The formula for calculating the max FIFO delay should be according to the formula I had shared in my last post.

Both, the internal line buffer and FIFO mean the same.

Best Regards,
AliAsgar