Vector 4 - Page 113

EXHIBIT 1I-24 PARALLEL PROTOCOL (““CENTRONICS TYPE")
The "Centronies Type"™ protocol uses parallel addressing through the programmable
8255 PPI Chip.
""" Strobe is RESET. The
T software interface is
£233
r{
EUTET
H
initialized
PORT 09H > —
(PIN 1) fooeeed
PRINTER PAPER
[ "Ready to Receive Signal"
— is checked by 8255 PPIL
£255 LI
- PORT 0AH | =
(IN1LY Y b Jeeceee
PAPER
PRINTER
- Data is lateched to print;er
mT SUFFER (triggered by strobe
255 L.y . 'I“l o signal).
1 PORT 08H - —
FAPER
PRINTER
H "Ready to Receive Signal"
UFFER
i
is
checked
by
8255
PPL
i Printer buffer is emptying
i and printer is printing.
2 Ll
"6
o k.
.
PORT 0AH i
PRINTER
T Data is latehed while
zw‘i? buffer empties. Printer
e
DATA
S
it
continues
printing.
L e TR T . T }”‘o'.:o'. ;'il
v h e ',..‘.' ., el | L‘-i'. . !i;'l:
§'a“
> — | il
PAPER
PRINTER