Salter Brecknell 7550 - Manual (Page 24)

Getting Weight – There are two (2) ways to get weight from the NCI 7550
In-Motion Conveyor Scale. "Standard" or poll method requires a command
to be sent from a PC to the scale to get weight, or "Burst" method which
requires that the PC is always ready to catch the weight automatically when
a package exists the scale conveyor. In case of error, the scale can be
commanded to return the last harmonized weight, units and status in either
standard or burst mode. Refer to Weigh-Tronix Serial Communications
Protocol Document SCP-16.
Standard / Poll Mode – With "standard" selected in the indicator as the
interface method, the in-motion scale requires a "P" command be sent to
request weight. The scale then returns the next harmonized weight, units
and status. "L" command will return the last harmonized weight, units and
status.
Burst Mode – While in the in-motion mode, autoprint changes functionality
to automatically print each time an in-motion weighment is made through
the in-motion logic. The default group for Autoprint is 1. (Displayed weight).
While in in-motion mode, the autoprint functions in the background.
Active X Control – This is a special purpose serial communications
control. It allows access to weight and status information from an NCI Model
7550 In-Motion Conveyor Scale from within the application. It does this by
handling all of the interface requirements defined in the NCI 7550 serial
communications protocol. Connect the scale to an available serial port on
your computer, set the required properties in the control and immediately
have access to weight, status and other scale functions.
This control provides an event-driven method of handling serial communi-
cations from the scale. Each control used corresponds to one serial port and
is used to access data from one scale.
Within the event-driven method, the application will be notifed the moment
an event takes place, such as when a complete weight message has been
received from the scale. In such a case, you can use the On-ScaleComm
event to determine which event occurred and then handled it in your
application program.
Since the WTComIM control uses Microsoft MSComm as a constituent
control, a lot of the details usually necessary to handle scale
communications are hidden and taken care of. This includes such items
as synchronizing received messages, parsing message strings, extracting
and converting weight and status information, handling communication
errors and detecting scale disconnect.
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