SPI Buses

The term SPI is used as a name for a number of interface buses;

Serial Peripheral Interface [SPI-bus], a 4-wire serial synchronous communications interface used by many microprocessor running at 1 megabaud.

System Packet Interface-3 [SPI-3], SPI-3 is a OTN standard interface for 10 Gbps point-to-point connections between two chips at OC-48 rates.

System Packet Interface-4 [SPI-4], SPI-4 is a OTN standard interface for 10 Gbps point-to-point connections between two chips at OC-192 rates.

SCSI-2 Parallel Interface [SPI-2], Small Computer Systems Interface [SCSI], 20MHz data rates. Note that the parallel SCSI interface is obsolete, and SCSI-2 defined an older interface than what was last used when the interface was in wide spread usage.

SCSI-3 Parallel Interface [SPI-3], Small Computer Systems Interface [SCSI], 40MHz data rates. Although this is a newer version of SCSI than the previous listing, in general the parallel SCSI interface has been replaced by Serial SCSI. So both of these references to the SCSI interface represent older peripherals that may still be in use but are no longer being produced with current products.

As with any common term or an acronym, there may be more than one meaning.
In this case the abbreviation SPI stands for both a serial interface and a parallel interface.
In the first case SPI refer to a chip-to-chip interface, while under SCSI the interface is a parallel cable interface.
So an interface bus used between ICs is completely different from an interface designed to drive a cable over three meters.
In addition the first serial bus listed is completely different from the follow-on serial buses.

The icon to Electronic Buses [below] will list all the different types of interface buses, interfaces that are both in-use and obsolete.
Each topic makes it clear if the electrical interfaces is out-dated, obsolete or still in common usage.

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Modified 1/25/12
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