Serial Protocols

up to 63 devices

1394b = 786 Mbps (now up to 3.2 Gbps)
can supply power to peripheral devices

can use direct memory access (DMA)

master device provides clock line

TTL or CMOS voltage levels and speeds (up to 70 Mbps)

SCK – serial clock (from master, shared by all chips)

MOSI – master output, slave input (shared by all chips)

MISO – master input, slave output (shared by all chips, slaves must have tri-state outputs)

can be longer and/or msb first based on slave chip

SPI send and receive subroutines in many programming languages
I2C
two wire interface (plus GND)
SCL – serial clock (bi-directional but typically provided by master)

SDA – serial data (bi-directional)

typically only master drives the clock

each chip has a pre-assigned unique address up to seven bits long

uses open-drain output drivers and pull-up resistors

TTL or CMOS voltage levels and speeds (up to 1 Mbps)
master issues a special start sequence and then sends the address of a specific chip

typically 8 data bits with msb first (depends on slave chip)

lower throughput than SPI but fewer wires

does not require multiple CS lines from master like SPI

I2C send and receive subroutines in many programming languages