Vaisala WS425FG - Manual (Page 40)

User's Guide ______________________________________________________________________
38 ______________________________________________________________________________
Diagnostic Operation
When a laptop computer is plugged into the TEST connector via the
DB-9 connection in the power supply, the following states exist:
A special Diagnostics Program for the laptop PC is provided that allows
RS-232 communications and sets the RTS and DTR lines to the desired
states.
RS-232 Data Format
Ultrasonic Wind Sensor WS425 F/G communicates via an RS-232
serial interface. The host system sends American Standard Code for
Information Interchange (ASCII) characters to the Ultrasonic Wind
sensor and waits for the appropriate response. The sensor transmits an
ASCII response to various interrogation commands within 250
milliseconds at 2400 bits per second. The sensor is programmable to
operate at data rates 2400, 4800, or 9600 bits per second (bps). The
communication link is via an RS-232 serial port interfaced to a fiber
optic modem utilizing separate cables for transmitting and receiving
data. Control characters and control procedures are compatible with
ANSI x 3.28 and ANSI x 3.66 respectively. The data format consists of
the following:
- 1 start bit
- 8 data bits
- 1 stop bit
- No parity
- 2400 bits per second, programmable to 9600 bps
- Full duplex
- Serial asynchronous
- Configures as Data Terminal Equipment (DTE)
RTS DTR Description of States
LO LO Normal host system operation (TEST, connector
unplugged).
HI LO PC talks to the sensor, host system is disconnected
LO HI PC talks to the host system, Sensor is disconnected
HI HI Host system is connected to the Sensor with the PC
listening to both the transmit and receive lines