Raytheon DIDS-400 Series Technical Manual page 169

DIDS-402-2AMI3
c. Insert or Delete Line - In the insert line function, the purpose of the
88-count ripple counter is to count 88 F{..6.) pulses. Since only one
character may be inserted per frame, the insert line function
requires 88 frame times to insert all 88 characters of a line.
When the SHIFT key is held-depressed, A is gated through NAND-gate
A23.11 and 2CTS clocks A8. 9 high. When the INSRT (or DEL) key
is depre ssed. the applicable flip-flop is set to enable gate AlS. 11.
The cursor is then located to enable NAND-gate A22.12 and thereby
latch A29. 3 high. The output of A29. 3 remains high for the duration
of the function and, as such, acts as an 88-count enable level.
The 88-count ripple counter then begins counting F(A) pulses which
occur once per frame. Simultaneously, the insert (or delete) char-
acter function is being performed once per frame by the insert (delete)
edit function circuitry. At the end of 88 frame times, the insert
(delete) line function is disabled by an 88-count complete level from
A28.12. This level sets the function-complete circuit and enables
the function to be terminated. Note that function complete latches
A29. 11 high to reset the ripple counter to a 0 count.
4-23.3. 10 Step-Down Function
.
The step-down cursor-control function moves the cursor from any charac- ..
ter position of a line to the same character position of the next line. In memory,
step down consists of delaying the cursor by 88 character times (one line time)
and causing
it
to appear in the CE register 1. 144 ms later than it has prior to
the initiation of the function (see figure 4-49).
To perform a step-down function, the cursor is located in 'memory by
sensing its presence in the cursor-located flip-flop of the CE register. When
the cursor is found, it is erased and then reinserted into memory after counting
88 characters. This delays the cursor by 1. 144 ms and places it on the next
horizontal line, immediately under where_ it was prior to the function.
When the step-down ( • ) keyis depressed, or when a VT control code is
received from the CPU without being preceded by an ESC code, A5.5 goes low.
The resulting high output from inverter A6. 6 is applied to NAND-gates AIS. 3 and
A15.6 and to 88-count enable-reset flip-flops A5. 9 (see figure 4-48) •.
When the cursor appears in the CE register, A15.3 is enabled and the
cursor is erased. Simultaneously, enable-reset flip-flop AS. 9 is set and the
88-count ripple counter begins counting CTS pulses. After 88 characters
(CTS pulses) have been counted, 88-count complete enables NAND-gate A15. 6
and the cursor is inserted into memory. The .88-count complete also enables
the function-complete flip-flop during 2CTS and during the following 3(CTS+1),
the step-down flip-flop is disabled.
4-127