The difference between synchronous and asynchronous communication

Here at Impulse we offer a wide range of serial communication boards and adapters; spanning across PCI, PCI-Express, ISA, PC/104 and PCMCIA buses, with communication interfaces including RS-232, RS-485, RS-422 and RS-530.

When you first delve into the world of serial communication it can be daunting – phrases such as parity bits, handshakes, clock signals and UART mean nothing to a beginner without a basic understanding of the serial communication theory.

If you look in our Industrial Communication section you will see under the Industrial Serial category “Asynchronous Serial Boards” and “Synchronous Serial Boards”. But what exactly is “asynchronous” and “synchronous”, and what are their differences?

The technical theory behind asynchronous and synchronous communication is effectively the same: device B needs to know when a transmission from device A has started, and if it was understood correctly. However, the difference lies in how the data transmission is broken down.

The difference between synchronous and asynchronous communication

In context, let’s look at this in terms of a conversation between two people. With asynchronous communication you would need to stop after every word to make sure your conversational partner understood what you have said, and they knew you were about to speak the next word.

With synchronous communication, you would establish with your conversational partner that you are speaking English, that you will be speaking words at measured intervals, and that you would be speaking a complete sentence or paragraph, before pausing to confirm they understood. You would establish with your listener beforehand that any odd noises you make during the conversation or between sentences (coughs, umms, errs etc) should be ignored.

Clearly the synchronous method is much faster, even though starting the conversation may take slightly longer. In fact, by replacing the start, stop and parity bits around individual words with start, stop and control (processing instructions and error checking) sequences around large continuous data blocks, synchronous communication is about 30% faster than asynchronous communication, before any other factors are considered.

All our serial communication boards, both synchronous and asynchronous, are designed and manufactured by our premium partner Sealevel Systems. There are several reasons why we chose Sealevel Systems.

Why Sealevel?

Sealevel’s products are designed specifically for use in mission critical systems, such as the ones seen in military, medical, public safety, transportation, oil and gas and aerospace industries. It’s of Sealevel’s utmost importance that their devices work every time in any application.

Whilst Sealevel’s cards do cost a little more than your run-of-the-mill alternatives, they are in fact much higher quality and a much better value for money. A closer examination of Sealevel’s serial communication cards reveal that is has more advanced features and is built to a much higher standard of quality. This is evident by the following features:
  • Circuit board laminate materialSealevel use a much higher grade board laminate material. It is much thicker which equates to a much stiffer and robust printed circuit, which can handle higher shocks, vibrations and environmental temperatures. The thicker board laminate, along with carefully designed circuit layout also makes the board less susceptible to electro-magnetic interference.
  • Robust Design – In addition to the board laminate material, Sealevel boards also use higher grade components. This allows their products to comfortably operate in applications that would cause lesser grade products to fail rather quickly.
  • Features – The Sealevel boards contain more features than their cheaper alternatives. This includes more modem signals present on the connector and more advanced set up options so you can be sure that the board can be configured successfully to work in your application.
  • Quality design and manufacturing – All Sealevel products are designed and manufactured in their 45,000 sq.ft facility in South Carolina, USA. Sealevel control every aspect of the design and conduct 100% testing to ensure every product that leaves their facility is in perfect wording condition. They’re also able to have complete revision control over their products to ensure that the product you buy will be exactly the same 10 years down the road.
  • Lifetime warranty Sealevel’s overall return rate is less than half a percent, including all returns where the customer managed the product, or where no problem was found. Sealevel are confident that their products will hold up to the rigors of your industrial application and stand behind their products by offering a lifetime warranty.

Learn more

Over the past decade Impulse has worked closely with Sealevel Systems to provide our customers with a highly reliable serial communications solution – both through our system integration services, or as a supply chain for the OEM and reseller market.

Impulse is an exclusive UK distributor for Sealevel products, most of which are available to purchase directly from our website.
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