Heathkit H9 Manual page 60

Pa s e ' 8
@
ments the + 12 counter, This addresses the next line of
information if the Auto Carry key is pressed in. If the
Auto Carry key is released, and end of line indication
wiII keep the counters from going to zero (the carry
pulse will not get to the + 12 counter) . The cursor will
then stay at the right end of the line.
A logic 1 from pin 2 of IC730 (5706 pin 9) causes the
carry and borrow pulses from the +20 counter to
cascade into the +4 counter. A logic i. from pin 2 of
1C724 (5707 pin 10) causes the carry and borrow
pulses from the +4 counter to cascade into the +12
counter. These two logic signals are generated in the
ROMs (IC724 & IC730) as a function of Vp' , Short
Form, Auto Carry, Scroll, +20 EOL (End Of Line), and
+4 EOL.
Vp' comes from the master TPU timing
(IC705B pin a) and it is logic 1 during re-
trace.
Short Form comes from the Short Form key
on the keyboard (S70a pin 10). When the
short form input is logic 1, the Terminal is
in the long form mode. When the short form
input is logic 0, the Terminal is in the short
form mode.
Auto Carry comes from the Auto Carry key
on the keyboard (5703 pin 10). The Termi-
nal is in the auto carry mode when the auto
carry input is logic 0.
Scroll comes from the scroll command
(lC747A pin 3). The scroll command is
logic 0 during a scroll operation.
+20 EOL comes from the RAM and counter
circuit board (5705 pin a). The +20 EOL
input is logic 1 when the count in the +20
counter is 19.
+4 EOL comes from the RAM and counter
circuit board (5707 pin 7). The +4 EOL
input is logic 0 when the count in the +4
counter is 3.
The EOL and auto carry signals defeat the C.U. +zo
signal whenever the auto carry function is not
selected.
Short Form
In short form, the cursor moves from the left to right
through a block of only 20 characters before being
returned to the start position of the next line. When it
fills up a block of zqO characters, it moves to the
top/start position of the next block of characters.
The +20 carry pulses increment the +12 counter if
the Auto Carry key is pushed in. This accesses the
entire first block of characters fwhen the +4 counter
outputs are zero). When the +12 counter reaches 11
(L011), and the +20 counter reaches 19 (11001), the
next count up pulse causes the +12 carry pulse to
increment the +4 counter to 1 (01). This process con-
tinues until all four blocks have been accessed.
A logic 1. from pin 2 of IC730 (S706 pin 11) causes the
carry pulses from the +20 counter to cascade into the
+ 1.2 counter. A logic 1 from pin 1 of 1C724 (S707 pin
8) causes the carry pulses from the +12 counter to
increment the +4 counter. These logic signals are also
generated as a function of Vp' , Short Form, Auto
Carry, Scroll, +4 EOL, und +20 EOL. Refer to the
"ROM Programs" section (in the "Semiconductor
Identification" section of the Manual) for the truth
tables for ROMs 1C724 (444-1.2) and IC730 (444-17).
Remember, the cursor always indicates the RAM loca-
tion where data will be written. Also, in long form,
data will enter the RAM in 80 character lines, while in
short form, data will enter the RAM in 240 character
columns. Refer to Pictorials 4-8,4-9, and +-t0 for a
summary of RAM locations and cursor movements.