
Serial Communication
Output Types
VT200/220 Technical Manual, Rev 1.00.01
55
Doc
#
TM-VT200/220-EN
The demand character may be programmed through
SETUP
>
SETUP 2,
setting
2.c
=65-90 (
A
-
Z
).
A
(41h) will generate and transmit the new Alibi number;
a
(61h)
will repeat the last Alibi number (in the case where the message was not received
properly).
6.3.7
EDP Protocol Output
Works With Port 2 (RS232 or RS485).
Transmits weight measurements to a host computer, according to the currently-
selected print format, with or without an ENQ prompt, and with or without an
ACK/NAK handshake (see Relevant Setup Parameters below).
The EDP protocol works when more than one indicator is connected to the host PC. It
is also more flexible than Print on Demand, allowing for more complex operations. It
can also transmit more than just the weight measurement shown on the display,
because it sends data according to the currently-selected print format.
Full Protocol Workflow
1.
Within 5 seconds of initialization, the PC requests data by sending an ENQ (05 h)
command. If it doesn’t send an ENQ, the indicator shows Error 30 (host not ready).
2. After the
( ) button is pressed, the indicator transmits weight information
according to the currently-selected print format, using the standard data block
composition (shown below).
3. Within 5 seconds of transmission, the PC either:
Acknowledges receiving the data properly, by sending an ACK (06 h)
command.
Notifies the indicator the data was not properly received, by sending a NAK
(15 h) command.
Does not respond, in which case the indicator shows error 33 (host does not
acknowledge).
4. If the host responded with a NAK command, steps 2 and 3 are repeated. The
number of repeats is unlimited.
Relevant Setup Parameters
3.1
– timeout control.
0
=No;
1
=Yes. Turning off timeout removes the 5-second
constraint in workflow steps 2 and 4. Errors 30 or 33 are never shown.
3.2
– handshake.
0
=No;
1
=Yes. Turning off handshake removes steps 4 and 5 of
the protocol workflow - the indicator sends data blocks on demand, without
waiting for a response.
3.3
– operator disable.
0
=No;
1
=Yes. If set to 1, any key pressed on this indicator
interrupts EDP communications.
3.4
– host enquiry.
0
=No;
1
=Yes. Turning off host enquiry specifies that the
indicator should send weight information continuously, not on demand.