Hello, From the manual shown bellow the address is 0x40 the measure temperature command 0xE3.

From the readback diagram
first master sends slave address and measure command,then We send slave Adress.

But we cant see in the diagram where is the measured data,how it transfered back?
The manual doesnt say what is MS Byte,MS Byte.

https://www.silabs.com/documents/public/data-sheets/Si7021-A20.pdf

Thanks.

 

I suppose the grey MSB and LSB are data from sensor, MSB+LSB -> 16 bit word

 

Hello,As shown there are A,Sr,R,NA,NA*

A-is acknowledge as said in AN0011 manual' During the next bit-period, the slave pulls SDA low (ACK)

Sr-SDA goes low while SCL high. It is allowable to generate a STOP before the repeated start. SDA can transition to high before or after SCL goes high in preparation for generating the START.

Regarding the NA and NA* shown bellow ,NA is not acknowledge .one device refuses to the communication of the other.

What is the difference between NA and NA* and what is the logic of putting them there?
Thanks.

https://www.silabs.com/documents/public/application-notes/AN0011.pdf

 

From datasheet:
*Note: Device will NACK the slave address byte until conversion is complete

 

NACK- is pulling SDA high.
but if we look in logical way,NACK means slave doesnt agree with the communication with master.
What is the purpose in that?
Thanks.

 

If conversion is done, slave will pull down SDA and sending ACK. There is two methods for communication, clock stretching by slave holding SCL down or waiting ACK from slave. Not very convient.