Sartorius FB Operating Instructions Manual page 68

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,
this will not generate an error
message.
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)
– Software handshake
(XON, XOFF)
68
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
(trans- ––– byte –––> (receiving
mitting ––– 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 in received,
it re-enables the transmitting
device to send data.
Receiving Device:
XOFF is transmitted after the
26th character has been stored.
To prevent too many control
commands from being received at
one time, XON is not transmitted
until the buffer has transmitted all but
14 characters.
If the device addressed does
not understand the control command,
the SBI receiving device activates
DTR (Data Terminal Ready)
after 6 more characters have been
received. The busy signal is
deactivated by XON (14 characters).
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
synchronously with the scale display,
or at defined intervals (see
application program descriptions
and auto print settings).
Data Output by Print Command
The print command can be
transmitted by pressing p/[PRINT]
or by a software command (Esc P).
device)
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 state.
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/[PRINT].