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DIDS-402 -2AM13
4-23.1.5 Decodes
Several decodes are connected to the CE register.
These decodes interpret
the following code s:
a.
A49.8, LF decode (0001010) - enables an automatic advance line
function each time the operator depresses the NEW LINE key.
b.
A48.8, BELL decode (0000111) - causes an audible alarm to be
activated each time the BEL control code is entered into memory
by the operator.
c.
A58.8, ETX decode (0000011) - used to determine whether the
operator has inserted an ETX into memory.
When ETX is decoded,
an ETXSR pulse is developed to enable the transmit circuitry.
d.
A64.8, DEL decode (1111111) - detects the pre sence of a DEL code
and performs a code conversion, jamming a code of 0011110 into
the CR register.
Thus, each time the DEL code is shifted into the
CE register, a short horizontal line is displayed on the CRT screen.
This line is used as a guide to prevent operators from entering data
into character slots already occupied by control code s
(1.
e., control
codes appear as blanks on the screen).
e.
A55.6, Control Code Decode (-00----) - When a control code is
shifted into the character entry register, a blank character
(0100000) is jammed into the CR register during 4(CTS+l).
This
re suIts in display of a blank character in the control code character
position on the CRT screen.
f.
A55.8, Control Code Decode (-00----) - detects the presence of a
control code in the CE register as well as the depre ssed condition
of the CONTROL key.
When the decode is enabled in this manner,
a lower case equivalent character is jammed into the character
readout register during 4(CTS+l).
4-23.2 Character Readout Register
The character readout (CR) register is part of the character generation
circuitry_
Character codes are entered into the CR register from the CE
-
register and held for one character time (from CTS to CTS).
During this time,
the monos cope beam is deflected to a specific character position on the monoscope
target to produce a visual character on the CRT screen.
The important fact to
remember about the CR register is that the digital code held in the register
determines which of 97 individual visual characters will be displayed on the
screen (see figure 4-38).
4-101/4-102
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