Appendix : Description Of The Rs 232 Link - Chauvin Arnoux C.A 25 Mode D'emploi

APPENDIX : Operation of the RS 232
The RS 232 output is a bi-directional interface which allows the instrument to
communicate with external peripherals.
The transmission signals of the data are at the RS 232 C standard which has an
amplitude between ± 5 V and ± 15 V.
- Level 1 = from -5 V to - 15 V
- Level 0 = from +5 V to +15 V.
The transmission rate is set :
- Speed = 1200 bauds
The format is fixed :
- 1 START bit/8 data bits/1 STOP bit, no parity.
Transmission code :
- All the transmission characters are in hexadecimal ASCII code.
Transmission is done on four wires :
- RxD Receive data (4 in the plug)
- TxD Transmit data (1 in the plug)
- CTS Data ready
- Ground
WARNING :
The RS 232 ground is common to the ground of the external sensor.
In the absence of data, the TxD output is always on 1 (between -5 and -10 V) and
the RxD input is on 1 or left free.
To allow the data to output from the instrument, the peripheral connected to the plug
must set a 0 level (between +5 and +15 V) on the CTS input.
When the CTS input is on 1, the instrument no longer emits, but if data remains to
be output when it is switched off, the latter are kept available to again be emitted
as soon as the CTS input returns to 0, the PRINT symbol remains lit as long as all
the parameters have not been sent.
This operation is above all made necessary for communication with printers that
have a low printing speed and which do not have a buffer memory.This interface
allows, among other things, printouts of measurement results, or the contents of
the programme memory, on a printer, from an instruction which can be local,
directly on the instrument, or remotely, from an external control unit.
(3 in the plug)
(2 in the plug)
94
. . . .
1
4
FRB female connector
of the tachometer seen
from the contact side.
2
3