Vector 4 - Page 105

EXHIBIT 11-20 ETX/ACK SERIAL PROTOCOL
This serial printer protocol uses the ETX/ACK type of "Software Handshaking".
The printer driver software is designed to send line information to the printer with
a terminating character. When the terminating character is acknowledged the
printer sends back an ACK byte on pin 2.
The ETX byte can be inserted into the data at the end of a line, end of a file or
any other location within the data stream. i.e. it is defined by the system
software.
[ Software may send
| W——- CONTROL SEQUENCE BUFFER initialization sequence.
. 48&5&%&@5 BRRREE Depends on printer
ART
PIN
3
>
—
protocol.
U1
PAPER
PRINTER
------ Software sends data with
T ETX ¢+ DATA End of Text Character
l - BUFFER
PIN 3 o
T
PRINTER
'",'i',; Buffer is full and printer
ETX + DATA Hy i inti
1 _ i 1s printing.
FEENEEED i
USART l"
PIN 3 o l!i&
s i
PAPER
PBINTER
ok [a Printer encounters an
— — 1l ETX character and sends
A BUFFER i i
A T ok an ACK (06H) character
USART||
—
:
flfliigig_
to
the
USART.
Printer
_ ! o .{.1'.1;.'!@ continues printing date.
PAPER
PRINTER
R USART sends data to
T
—
DATA
A
.'
o
.
N
" | di¥lfi}§ _pureeR | i pri neter buf'f er. Printer
USART PP AT [T ;r%iizai!%fl continues printing.
PIN 3 o li:“i{ii gf
il
PAPER
PRINTER
I 5-14