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Hi Team,
Please allow me to ask you about EOM function.
How fast is the EOM data updated ?
The reason why I'm asking is that when user want to draw eye opening themselves, I wonder if SPI interface would be faster to draw eye pattern compared with the SMBus because of the clock speed.
However, if the EOM data update speed is not fast enough, user would need to wait until the data is updated as noted in the datasheet.
Would customer have merit using SPI when using EOM function ?
Best Regards,
Kawai
**6/30: Edited with correct calculation of time per data point**
Hi Kawai-san,
The udpate for the entire EOM can be calculated by taking the number of data points and multiplying by the amount of time spent at each data point.
When I checked with our design team, the amount of time spent on each data point is approximately 33 us. Since the EOM is a 64 x 64 grid, this means that all the EOM data is ready after 33 us x 4096 = 135 ms.
When SPI is operating at maximum frequency (20 MHz), each 17-bit transaction takes (1/20MHz) x 17 = 0.85 us, which is less than the amount of time per data point computation (33 us).
Since SPI transactions can be completed and read-back is faster than SMBus, I believe there is merit in your logic that you will be able to view the EOM pattern quicker with SPI instead of SMBus regarding EOM.
However, please note that the increased amount of time needed for SMBus to read back EOM data does not result in a significant difference regarding the eye observed. Therefore, I would offer the suggestion that, while SPI is quicker, both control interfaces are suitable for reading back the EOM data.
Regards,
Michael