regarding spi interface

[gopal_kmu54]

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?
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?

 

[sunny1986]

Yes it is bi directional please go to wiki site and search spi........read it

 

[FvM]

all the slave SDO are tied together and fed to the SDI and slaves are controled through individual slave select line?

That's the way to do it. SPI slaves are required to expose a tri-statetable data output (MOSI), it's only activated for the selected device.

 

[ckshivaram]

The Serial Peripheral Interface or SPI-bus is a 4-wire serial communications interface used by many microprocessor peripheral chips operating at full-duplex. The Serial Peripheral Interface (SPI) circuit is a synchronous serial data link [1 megabaud] setup as a Master / Slave interface, operating as a full-duplexed protocol.

The SPI bus can support up to 10Mbps. The SPI bus specifies two control lines Chip Select [CS] and Serial ClocK [SCLK] and two data lines Serial Data In [SDI] and Serial Data Out [SDO]. There may be other naming conventions such as MOSI [Master-Out-Slave-In], MISO [Master-In-Slave-Out], or SS [Slave-Select] that are used by Motorola. Devices may not have or use all four of the I/O pins. SDI [MOSI] may not be present if a device does not require an input [ADC for example], or SDO [MISO] may not be present if a device does not require an output [LCD controllers]. One SPI device acts as the SPI Master by controlling the data flow [generating [SCLK] and asserting device select [CS], then receives and or transmits data via the two data lines.

If the devices on the SPI bus have a chip-select signal it is possible to connect many ICs to the same SPI bus in parallel. If there is a chip-select (CS) signal in use, it can be driven by a spare microcontroller general-purpose output. Every IC connected to the bus needs it's own chip-select signal line. The SCI bus which is used for Asynchronous Serial Communication may be seen next to the SPI bus on a microprocessor.