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The immediate print output is always transmitted with a carriage return and
line feed. If the balance is set to a specific number of line feeds, these will be
transmitted with a carriage return.
The RS-232 Interface Hardware
Although Setra balances can communicate with almost any RS-232 device,
the built-in interface does not include the complete protocol. Only the
transmit and receive lines of the standard interface are used. This should
not present any interfacing problems in most applications.
The data format is:
1 start bit
8 data bits including parity
1 stop bit
10 bits per frame (framing errors ignored)
Note:
The balance will transmit using the parity selected; however it does
not check the parity it receives. Use an RS-232 cable to connect the
external device to the balance, or construct one following the in-
structions below.
Connect a high quality, shielded cable with a DB9S (D-Subminiature 9 pin
female connector) using the following pinout:
1 2 3 4 5
PIN
DESCRIPTION
• • • • •
2
TXD - scale transmits data
• • • •
3
RXD - scale receives data
6 7 8 9
5
GRD - signal ground
Note:
“Handshake” signals, such as “Clear To Send” (CTS), are not used. The
peripheral must have a minimum buffer (15 characters).
Shielded cables must be used with this unit to ensure compliance with the
Class A FCC limits.
Computers which require handshaking need a connection between two
pins on the computer’s connector named DTR and DSR (Data Terminal
Ready and Data Set Ready). CTS may also need to be jumpered to RTS at
your computer interface (Clear To Send and Request To Send). The maxi-
mum recommended cable length is 15 meters. The cable can be longer if it
has < 2,500 pF capacitance. The load impedance of the device connected
should be between 3,000 and 7,000 ohms with no more than 2,500 pF shunt
capacitance.
