DS90UB940-Q1: what is the pulse after ACK

Sherry Liang

Dear team,

The first waveform is SDA, and the second is SCK. SOC wants to write 0x50 to the register 0x68. But after every ACK there will be a pulse(marked by green box). I didn't find related description in the datasheet. Could you please tell me what is this pulse?

Thanks & Best Regards,

Sherry

over 6 years ago

0 Charley Cai over 6 years ago

TI__Genius 12866 points

Hi Sherry,

This looks like the master releasing SDA after ACK. Does this interfere with I2C read/write operation?

Best Regards,

Charley Cai

0 Sherry Liang over 6 years ago in reply to Charley Cai

TI__Genius 10255 points

Hi Cai,

It is the write operation. Our device is in slave mode. And the SOC is in master mode. This operation is that the SOC wants to write 0x50 into the 0x68 register. So the first 8 bits is our device's I2C address--0x58, the 9th bit is ACK. And then the second 8 bits is the register's address--0x68, the 9th bit is ACK,.and the third 8 bits is the data that SOC wants to send to the 0x68 register.

Thanks & Best Register,

Sherry

0 Charley Cai over 6 years ago in reply to Sherry Liang

TI__Genius 12866 points

Hi Sherry,

Is the write operation successful?

Best Regards,

Charley Cai

0 Charley Cai over 6 years ago in reply to Charley Cai

TI__Genius 12866 points

Please let me know if you still have question on this.

This pulse should be the I2C master releasing SDA after ACK.

Best Regards,

Charley Cai

0 Sherry Liang over 6 years ago in reply to Charley Cai

TI__Genius 10255 points

Hi Cai,

The write operation is successful. This pulse is generated by our device, right?

Thanks & Best Regards,

Sherry

0 Charley Cai over 6 years ago in reply to Sherry Liang

TI__Genius 12866 points

Hi Sherry,

If the SoC is in the master mode, the pulse is generated by the SoC.

Best Regards,

Charley Cai

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DS90UB940-Q1: what is the pulse after ACK