regarding spi communication

[gopalakrishnan]

hai to all

1. is it possible to communicate more than 128 devices through spi? if yes what is the limit of peripheral devices to be interfaced through spi?

2. is it possible to intercommunicate between the slaves?

3. more than one slave will communicate the master is it happens?

4. is it possible to arrange pic in cascaded manner through spi communication?


with regards
K.Gopalakrishnan

[Ttelmah]

1). At heart, yes, _but_ it becomes down to you generating the CS lines, and some form of bus transceiver will be required (the 'fanout' of a standard output, varies with frequency, and drive voltage, from only about 10, up to potentially several thousand devices).
2) No. SPI, is a master-slave interface.
3) Since it is master-slave, master always initiates the transaction, and it controls the selection of devices.
4) Yes. You could design a SPI protocol, that passes a packet, which then triggers the transmission of a packet on a second SPI bus.
Why the reference to '128'. There is no address numbering in SPI, 128, is the limit in I2C, when using 7bit addressing. Nothing to do with SPI...

Best Wishes

[gopalakrishnan]

Thank you very much. When do we use SPI and when do we use I2c ? What are the basic differences ?

[bkamen]

http://en.wikipedia.org/wiki/Serial_Peripheral_Interface_Bus

http://en.wikipedia.org/wiki/I2C
_________________
Dazed and confused? I don't think so. Just "plain lost" will do. :D

[gopalakrishnan]

hai to all

what are spi extenders? what is the use of it?

is spi communication is bi-directional? if yes when i connect multiple slaves with master if individual slave will communicate with the master? if so when more than one slave will communicate at the sametime to the same master what happens? where slave will communicate to the master with some id's mentioned during program?
or
all the slave SDO are tied together and fed to the SDI and slaves are controled through individual slave select line?

kindly clarify my doubts?

[Geps]