Synchronization
During data communication between the
scale and an on-line device (computer),
messages consisting of ASCII characters are
transmitted via the interface. For error-free
data communication, the parameters for
baud rate, parity, handshake mode and
character format must be the same for
both units.
You can set these parameters in the
Setup menu so that they match those of
the on-line device. You can also define
parameters in the scale to make data
output dependent on various conditions.
The conditions that can be configured are
described under each of the application
program descriptions.
If you do not plug a peripheral device into
the scale interface port, no error message
will be generated.
Handshake
The scale interface (Sartorius Scale
Interface = SBI) has transmit and
receive buffers. You can define the
handshake parameter in the Setup
menu:
– Hardware handshake (CTS/DTR)
– Software handshake (XON, XOFF)
Hardware Handshake
With a 4-wire interface, 1 more
character can be transmitted after
CTS (Clear to Send).
Software Handshake
The software handshake is controlled
via XON and XOFF. When a device is
switched on, XON must be transmitted
to enable any connected device to
communicate.
When the software handshake is
configured in the Setup menu,
the hardware handshake becomes
active after the software handshake.
The data transmission sequence
is as follows:
Scale ––– byte –––> Computer
(transmitting ––– byte –––> (receiving
device) ––– byte –––> device)
––– byte –––>
<––– XOFF –––
––– byte –––>
––– byte –––>
…
(Pause)
…
<––– XON –––
––– byte –––>
––– byte –––>
––– byte –––>
––– byte –––>
Transmitting Device:
Once XOFF has been received, it prevents
further transmission of characters.
When XON is received, it re-enables the
transmitting device to send data.
Receiving Device:
To prevent too many control commands
from being received at one time, XON is
not transmitted until the buffer is almost
empty.
Activating Data Output
You can define the data output parameter
so that output is activated either when a
print command is received or automatically
and synchronous with the scale display
or at defined intervals (see application
program descriptions and auto-print
setting).
Data Output by Print Command
The print command can be transmitted by
pressing p or by a software command
(Esc P).
Automatic Data Output
In the “auto print” operating mode, data
are output to the interface port without
a print command. You can choose to have
data output automatically at defined print
intervals with or without the stability
parameter. Whichever parameter you
select, the data will be output as the
readouts appear on the scale display.
The display update frequency depends
on both the model of the scale and the
current operating status.
If you select the auto print setting,
data will be transmitted immediately the
moment you turn on the scale. In the
Setup menu you can configure whether
this automatic output can be stopped and
started by pressing p.
105
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