Raytheon DIDS-400 Series Technical Manual page 186

DIDS-402-2AMl3
4 -24. 6. 1
LWL
Pulse
During CTS of the 79th character of the line, Al3.6 goes low to produce
a 'not' last word of line output. This pulse is coincident with the CTS pulse
which shifts the last displayable ·character into the CR register.
The LWL pulse is used to simultaneously inhibit the step-right function
and enable the advance-line function. Thus, LWL essentially prevents the key-
board or buffer register input circuits from entering any characters during
retrace since an entry results in lost data.
4-24.6.2 EOL Pulse
During 3CTS of the 80th character of the line, A2.6 goes high to produce
an end-of-line pulse. This pulse is employed to disable the insert and delete
edit functions at the end of each horizontal line.
4-24.6.3 Horizontal Drive and Blanking
On the trailing edge of CTS of the 80th character on the line, the Display
Terminal enters horizontal retrace. The horizontal retrace time is eight-charac-
ters wide (104 tJ.s) and is developed by NAND-gate A8.3. The H DRIVE output of
A13.3 is used to saturate a transistor on the horizontal deflection amplifier and
allow the drive pulse. to collapse. During this same time, the blanking output
cuts off the video amplifier so that the return of the CRT scan to the left side
of the screen will not be visible.
4-24.6.4 First Word of Line (.6.)
The .6. pulse is produced by AND-gate A2.12 during CTS of the 87th charac-
ter of the line. During.6., the last character of horizontal retrace is transferred
into the CR register. During the following 3(CTS+2) to CTS of the 88th character,
the retrace character would be displayed (if it were possible) and the first dis-
playable character would be transferred into the CE register. On CTS of the 88th
character, the first displayable character is shifted into the CR register and
displayed during3(CTS+2) to CTS of the 1st character.
Note that during vertical retrace, a L::. pulse is not produced when V DRIVE
goes low. An F(L::.) pulse is developed in this character slot to indicate the begin-
ning of a new frame.
4-24.7 Line Counter
The line counter (figure 4-62) counts the number of horizontal lines per
frame. There are 13 displayable line s and an extra 88-character line (line 14)
which is used for vertical retrace. The line counter is clocked by a pulse during
CTS of the 80th character of each line which is developed by the character
counter.
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