I2C protocol

[younus_noman]

In I2C protocol, when we say

i2c_wirte(address)

Is this address received by all the slaves or it is only received by one slave with the above address specified?

Noman

[asmallri]

[Mark]

Following a start condition, the next 8 (or 10 depending on addressing) bits are loaded into the SSPSR register. If these match the value in the SSPADD then the data is transferred to the SSPBUF register. You do not have access to the SSPSR register so in reality the write condition will only be received by the device whose address matches.

[younus_noman]

Mark,

So this means that the address is recognized by the hardware and not the software.

Thanks

Noman Younus

[Mark]

Well you can recognize it in software but it is the hardware match that allows you to read the data and any subsequent bytes.

[valemike]

I think he means:

Will the MSSP module (hardware) recognize it, and filter it before it even gets down to the software (e.g. mssp interrupts, mssp state machine, etc.)?

So yes, only your hardware will know that there is an address mismatch, and is transparent to your software. Only when there is an address match will the MSSP module act, and set the bits that trigger your i2c isr routines.

[Mark]

Note that if you enable interrupt on start and stop that you will get those interrupts whether your address matches or not.