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DIDS-402. -2.AM13
The step-left function is perform.ed each tim.e the step-left ( -
) key is
- depressed or each tim.e a
~BS
control code is received from. the CPU without
being preceded by an ESC code.
To perform. a step-left function, the cursor is located in m.em.ory by
exam.ining the output of the delay line during CTS.
(Rem.em.ber that the cursor
is the only bit in m.em.ory that is high during CTS.) Once located, the cursor is
erased before entering the CE register and inserted at the output of the CE
register.
In essence, the cursor bypasses the shift through the CE register.
The tim.e 'saved' in this manner allows the cursor to appear 13 tJ.s earlier than
it had previously.
When the step left ( - ) key is depressed, the input to step-left flip-flop
A32..6 goes low.
PB3, which occurs from 0 to 16 m.s later, sets A32.. 6 high
to enable one input to NAND-gate A46. 12..
From. 0 to 16 ms later, the cursor
appears at the delay line output during CTS.
The output of A46. 12. (a low) is
applied to A3. 8 of the input display logic and AI. 8 of the output display logic.
This places a high at the entrance to the delay line during CTS (the- cursor) and
erases the high previously present at the CE register input.
On
the trailing edge
of 2.CTS, the function complete flip-flop is
r~set
and during 3(CTS+1), the Function
Complete level disables the function.
The" BS control code (decoded in D3) per-
form.s the sam.e function except that the PB3 clock pulse is not required.
This
eliminates from 0 to 16 ms of the time norm.ally required to accoIIlplish the
step-left function.
4-2.3.3.4 Advance-Line Function
The advance-line, cursor-control function moves the cursor from. any char-
acter position on a particular line to the firs;t character position of the next line.
In meIIlory, advance line causes the cursor to appear in the CE register from
104 to 1144 tJ.s later than it had prior to the advance-line function.
The two ex-
tremes occur when the cursor is associated with the last character of a line
(104 tJ.s) or with the first character of the line (1144 tJ.$).
All other character
positions fall som.ewhere in between these two extrem.es (see figure 4-42.).
The advance-line function is performed each tim.e one of the following
occurs:
a.
The operator depresses the ADV LINE or the NEW LINE key_
b.
A line feed (LF) control code is detected in Dl during transm.it
c.
A line feed (LF) or carriage return (CR) control code is received
from. the CPU without being preceded by an ESC code
d.
An ETX control code is received from. the CPU to terrn.inate the
receive mode (Advance Line at
En~
of Receive Mode option)
4-112.
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