topic SPI and I2C usage in Classic/Legacy CodeWarrior

SPI and I2C usage

vishaka_maithil — Mon, 27 Sep 2010 18:53:10 GMT

Hi friends,

I would like to be answered for why and when do we use SPI and I2C. I have RTC ICs that has SPI and I2C Interfaces to my controller.Which one should be choosed between is what Iam confused with.

I would appreciate for any reply as soon as possible.

Thank you in advance..

Re: SPI and I2C usage

Witztronics — Mon, 27 Sep 2010 23:36:26 GMT

manasa,

Although in many cases either will do, there are significant differences. Usually the requirements of the system will drive the design to one or the other. If this is not the case, then most likely you can use either with similar results.

some SPI advantages:

full duplex

up to 70 Mhz (but not all devices)

not limited to 8-bit words

no slave addressing

no arbitration required due to single master

some I2C advantages:

2-wire vs 4-wire (some version of SPI only require 3)

all slaves use same two wires

longer distances

communication is "acknowledged" by receiving end

multiple master is easy to implement

From experience, I can tell you that not all SPI is the same. I have run into many instances where one is not compatible with the other. For example, some SPI memory devices use a different clock polarity than others and sometimes it does not agree with the one offered in the micro.

Re: SPI and I2C usage

vishaka_maithil — Tue, 28 Sep 2010 17:14:28 GMT

Hi Wiztronics,

Yes, you are correct that it depends on the system requirements to choose a right communication bus. Thank you for the reply.