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DIDS-402 -2AM13
The function of these keys is to perform a specific control action other than
producing visual characters.
With two exceptions (END and NEW LINE), these
keys acting alone do not produce the digital coding necessary to develop visual
characters.
Note however, that the entry control keys have a pronounced effect
on the coding produced by a character key depression, and therefore on the
visual character producec1
When any character key is depressed, a magnetically actuated reed switch
within the key allows current to flow through a branch of the keyboard matrix.
The matrix output, vv .. dch· consists of a specific 7-bit digital code. is coupled over
seven output lines designated FXl, FX2, FX4, FX8, FY 1, FY2, and FY4.
In
addition to the digital code output, a strobe level (INTERLK) is produced each
time a character key is depressed.
This strobe pulse is used to determine that
a character key has been depressed and subsequently to strobe the 7 -bit digital
code into the character entry register.
Most of the character keys have three separate binary codes that may be
developed, depending upon the circumstances present when the key is depressed.
The three codes represent the lower case, upper case, and control modes.
A
complete summary of character keys and their coding is listed in table 4-3.
LC, UC, and C are defined as follows: the code opposite LC is produced when
only the character key is depressed; the code opposite UC is produced when the
character key and the SHIFT key are depressed simultaneously; and the code
opposite C is produced when both the character key and the CONTROL key are
depressed simultaneously.
The codes listed in table 4-3 are the actual inputs
to the character entry register under the circumstances indicated.
The charac-
ter entry register is de scribed in the following text.
Table 4-3.
Keyboard Characters and Coding
Ke-y
Mode
ASCII Code
~
C
UC
LC
011 1100
CD
C
UC
010 0001
LC
011 0001
GJ
C
UC
010 0010
LC
011 0010
[I]
C
UC
010 0011
LC
011 0011
C
[I]
UC
010 0100
LC
011 0100
4-25
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