June 25, 2008

HyperTerminal & Code Page 437

Code Page 437 Link: http://en.wikipedia.org/wiki/Code_page_437

When you are setting up and testing a communication protocol you may need to send and receive some protocol flags such as SYN, ACK, STX, DLE, etc. In Windows (I am not sure if Vista has it) you can make use of the tool called HyperTerminal to do the testing. For more details on HyperTerminal refer to
a) http://technet2.microsoft.com/windowsserver/en/library/02c2459f-5b84-45fb-afab-610374d359941033.mspx?mfr=true
b) http://www.tech-faq.com/hyperterminal.shtml


After you have figured out how to use the HyperTerminal you will be wondering what are the characters that appear on the screen. Obviously they correspond to some ASCII value but what the values are is a big question. To find out that you can refer to the very first link in this post.

That link really helped me and my project mate when we were testing an asynchronous serial RS232 communication. Infact if we hadn't found it using Google we would have been stuck with our project for ages.

From the chart in the link you can interpret the ASCII value. You might also question how on earth can I send a for example DLE flag especially when none of the characters are present on the keyboard.

Here is the formula:
"Ctrl" + alphabet
alphabet = corresponding ASCII value of {64 + ASCII value corresponding to the flag}

- To send DLE (ASCII value = 16), find the sum of 64 and 16 (64 + 16 = 80).
- Now check which character corresponds to the ASCII value 80 in the chart. In this case it is 'P'.
- So press "Ctrl + P" to send a DLE.
Note: Although 80 corresponds to P in CAPS you can just press Ctrl + p (in small) as it works. I have never tested with capital letters.

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