ID #1020

I need to use a custom speed on your PCI card, can I do it?

The serial ports on the PCI-devices of VScom provide many more speed configurations as are offered for selection in typical programs. Especially when connecting very special hardware there is always the question, whether the requirements of the hardware are supported by the serial ports. To get your answer quick just use the new Online Speed Calculator for VScom products.


There is a formula to calculate the bitrates, which can be configured on serial ports. This is for serial ports based on UARTS 16C450 and compatible chips. Such are used in most products on the market.

Speed = (16*Bmax) / TCR / (CPR / 8) / Divisor, divide from left to right.

Speed : resulting bitrate (bit per seconds)
Bmax : maximum bitrate in 16C550 mode (bit per seconds)
TCR : signal sample count
CPR : Prescaler
Divisor : a 16 bit Integer number

The Divisor always ranges from 1 to 65535.

These parameters have different allowed ranges or values on certain .

VScom L-Series
VScom H-Series VScom Industrial VScom PCI Express
Bmax 921600 Bmax 921600 Bmax 921600 Bmax 3906250
TCR 16 TCR 4 to 16 TCR 16 TCR 4 to 16
CPR 8 CPR 8 to 255 CPR 8 CPR 8 to 511

You need to try parameter configurations to find your target bitrate as the result, TCR should be as high as possible. A resulting bitrate is generally considered acceptable, if the deviation from the target bitrate is less than 2%.

For the L- and Industrial series the formula reduces to
Speed = Bmax / Divisor
Divisor = Bmax / Target
Test the integer numbers nearest to the resulting Divisor in the upper formula.

Also note: On some products the Bmax may be changed by a configuration jumper.


And here are instructions how to use the speed inWindows. They are for the programmers of your application. How to configure the serial card for my baudrate? It is not available in the Device Manager.

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Last update: 2016-02-22 18:21
Author: Support
Revision: 1.2

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