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Parallel communication
Parallel communication
[1] In data transmission, parallel communication is a method to convey many binary digits simultaneously ("parallelly") via many conductorsm unlike serial communication, which conveys 1 bit at a time ("serially"); a distinction to characterize communications link.
It uses a clock signals for timing synchronously., i.e. data is transferred according to the clock's timings.
2 usual timing signals are:
Clock signal: continuous repeating pulse, acts like a metronome.
Strobe signal: "Attention" signal that only executes at specific moments.
[1] Another contrast of parallel and serial communication channels is the number of electrical conductors used at the physical layer to convey bits. Parallel communication implies more than 1 such conductor.
E.g., an 8-bit parallel channel conveys 8 bits/byte simultaneously, but a serial channel convey the same bits sequentially, one at a time. If both channels operated at the same clock speed, the parallel channel would be eight times faster. A parallel channel may have additional conductors for other signals, such as a clock signal to pace the flow of data, a signal to control the direction of data flow, and handshaking signals.
[1] ICs has always widely used, peripheral buses, and memory devices like RAM, have always widel yparallel communication. Unlike computer system buses evolve: parallel communication was often used in buses, whereas serial communications are prevalent in modern computers.
Upsides
Upsides
Downsides
Downsides
Unsuible for long distances: The clock and data signals aren't ideally aligned along wires. Despite being simultaneously, the signals move at a finite speed, so the clock edge and data bits can arrive slightly shifted relative to each other, causing the receiver to sample data at wrong moments. Such delay difference is minot in short distances.
[M1] parallel data transmission timing diagram
Data transferring diargam
Data transferring diargam
This timing diagram depicts a physical lane as rows of data, carrying bits constantly switching between 1 and 0 at high speed.
The intersection of the 2 signals is the moment where the signal changes from 1 to 0 and vice versa.
Each row has 2 data to depict all possible scenario (1 or 0) simultaneously IO a specific one.
hexagonal lines to represent data transitions where signal states change.
The red dotted line indicates the sampling point, aligned to the clock signal's rising edge.
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Applications
Applications
Computer processors and internal buses
Computer processors and internal buses
Motherboard traces: In computers, data must trravel instantly between the CPU, RAM, and GPU. These systems use wide parallel buses of 32 or 64 bit channels.
Internal registers: Procesors' ALUs in process data chunks, like 64-bits, in parallel to maximize caluclating speed.
Traditional computer peripherals
Traditional computer peripherals
PCI (peripheral component interconnect): Older desktop expansion slots used parallel architecture to connect sound cards and network cards directly to the motherboard.
ATA / IDE hard drives: Older ribbon cables inside computers sent 16 bits of data simultaneously to hard drives before serial options took over.
IEEE 1284 (printer ports): Legacy printers used thick parallel cables to receive data quickly from a computer.
References
References
[1] Wikipedia
[2]
My materials
My materials
[M1] ELE8940 RS232
[M2]
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