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TOPIC: Key Mapping Problem
#1615
Key Mapping Problem 12 Years, 9 Months ago  
I am using Absolute Telnet to connect to a PDP8 computer via an async port. I can connect fine but the key mapping is all wrong. I type a "w" and get a "s". I Type a "v" and get a "r". Here are the charecters I get:

Keyboard/Display

1234567890-= echos 1230123890)9
qwertyuiop[] echos qsarpyqikp[yx
asdfghjkl;' echos as`bchjkh;#
zxcvbnm,./ echos zxcrbji(*+

Is this a simple key mapping problem?

[size=1][ February 26, 2008, 02:36 PM: Message edited by: Brian T. Pence ][/size]
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#1616
Re: Key Mapping Problem 12 Years, 9 Months ago  
Very interesting.

It is not a key mapping problem.

If you look carefully, you'll notice that there is a pattern to which characters are wrong. Each of the mixed-up characters is missing it's third least-significant bit.

For example, the character q come through ok because it's third-bit is already 0. Other letters echo differenty because their third bit is stripped.

letter decimal binary echos decimal binary
q 113 1110001 q 113 1110001
w 119 1110111 s 115 1110011
e 101 1100101 a 97 1100001
4 52 0110100 0 48 0110000
5 53 0110101 1 49 0110001

I have no experience with PDP8, so I'm not sure where to guide you, but hopefully this insight will lead you down the correct path. I have a feeling that you have serial hardware problems. Perhaps you need a new PDP8?
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Brian Pence
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SSH , SFTP, and Telnet in a tabbed interface for Windows XP, Vista, Mobile, and others
 
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