Serial Communication
Output Types
VT400 Technical Manual, Rev. A5
47
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UM-VT400-EN
Full Protocol Workflow
1.
Within 5 seconds of initialization, the PC requests data by sending an ENQ (05h)
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 (06h)
command.
Notifies the indicator the data was not properly received, by sending a NAK
(15h) 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 this option is turned on, an indicator may
interrupt the protocol by pressing any key on the indicator keypad.
3.4
– host enquiry.
0
=No;
1
=Yes. Turning off host enquiry specifies that the
indicator should send weight information continuously, not on demand.
Data Block Composition
Character/s Description
STX (02h)
Start of transmission.
ASCII (any)
ASCII data identical to the data printed.
ETX (03h)
End of transmission.
BCC
Block check character (XORSUM of all data characters STX, ETX inclusive).
6.3.7
Remote Printer Output
Works with Port 2 (RS232 or RS485). Used to transmit the data printed on the local
printer to a remote printer. No handshake is required.