High Speed Serial Interface, Bits and Baud Rates

Thursday, September 17, 2020

STX Technology Utilizing High Speed Serial Interface

As we move into a new technological age, consumers and businesses are demanding better performance from digital communication. Technological innovators are responding by locating ways to increase communication data rates with modifications to board hardware. STX Technology welcomes the opportunity to attain and sustain maximum bitrates in our electronic componentry for clients that require faster transmission speeds in their products.  

We explore the evolution of High Speed Serial Interface (HSSI) and Baud Rates below within the context of STX Technology’s advanced technological solutions.

High Speed Serial, Bits and Baud ratesHigh speed serial, bits and baud rates

High Speed Serial Interfaces address the need for high speed communications operating above 200k Kbps. Using a DTE/DCE interface defined by the RS-232C standard within the HSSI framework leads to smaller device footprints, higher data throughput and lower power requirements. Due to the highly configurable qualities of serial protocol, adding high speed serial boards within units at close range is only limited by the requirement of  having both the DTE and DCE configured at the same speed. The speed with which data is communicated over a serial line indicates the baud rate or signal unit which is expressed in bits-per-second. Older baud rates, for data transfer where speed is not a critical factor typically transmitted at speeds of around 9600 bps. More recently, baud rates of serial transmission can be programmed by accessing the serial register and producing rates that easily exceed this.

While standard baud rates were communicated at rates in the lower tens of thousands of Kbps, HSSI standards allow serial data rates that operate at speeds of between 300K-900K Kpbs with a high end serial modem.

Standard Baud rates alongside newer versions can be illustrated in the table below:

 Standard Baud Rate

(bits and kb/second)

Time/ Bit 


High Speed Baud Rate

(bits and kb/second, mb/second)

Time/ Bit


1200 or 1.2Kbps

833.3 μs

230 400 or 230.4 Kbps / 23 mbs

4.34 μs

2400 or 2.4 Kbps

416.7 μs

460 800 or 460.8 Kbps / 46 mbs

2.14 μs

19 200 or 19.2 Kbps

52.1 μs

921 600 or 921.6 Kbps / 69 mbs

1.6 μs


High Speed Serial Baud rates 

The input of multiple serials can be configured into many of STX Technology’s units to increase transmission speeds. For example, we recently designed a unit that incorporated a module capable of a data transfer rate of 230 400 baud, the equivalent of 230Kbps or 23 Mbs.

The World of Big Data

A transition from parallel buses to High Speed Serial buses has the combined benefits of increased performance while reducing size and power. High Speed Serial buses are being integrated with higher frequency as data communication requirements increase. For example, demanding applications like motion control or large industrial network systems are calling for the capabilities of innovative Ethernet technologies such as etherCAT. Ethernet is a synchronous system, unlike the RS 232 protocol which is asynchronous. In a synchronous systems, instead of the clock provision as  a discrete wire, the clock is encoded into the data stream. The advantage being, this keeps the number of wires to a minimum yet allows high speed data transfer.

The table below illustrates the main differences between the RS-232, RS-422 and RS-485 interfaces. 






Transmission Line Configuration


Single ended



Maximum number of drivers




Maximum number of connected receivers




Maximum Distance

15 metres at 9600 bps

1200 metres at 9600 bps

1200 metres at 9600 bps

Driver Output (depends on length of cable and load)

5-25 V

2-6 V

1.5 – 6 V

Driver Load

<3k Ω

100 Ω

60 Ω





By comparisont, a CAN interface is designed to allow devices to communicate to each other without having a single host PC. CAN which is used with CAN Bus is a differential two wire interface predominantly targeted for microcontroller based applications such as those implemented in automotive, medical and networking industries. For more information on CAN Bus and its' application please refer to our earlier article here.

High Speed Serial is an option in many STX Technology products so if you require high speed data transfer to assist in the management of your industrial environment,  give one of our experienced team a call. Here to support your ideas.


Find a video on HSSI here

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