Vaisala CL31 - Page 58

USER'S GUIDE____________________________________________________________________
56 __________________________________________________________________ M210482EN-D
The lines use the 7-bit USASCII character format. Both the UPPER and
lower letter cases can be used.
The standard operation of the serial lines requires no handshake signals.
A communication port, in other words the serial line, has the following
two internal states (see Figure 21 on page 57).
-
CLO
SED: This is the transmitting state of a measurement data
message. In this state, messages are transmitted as a response to a
polling input string or automatically at predetermined intervals,
depending on the settings (message transmission). User commands are
not accepted, except for the
open command, which turns the line into
the OPEN state.
- OPEN: This is the user dialog state. In this state, the device responds
to user commands and command input is echoed. A command prompt
CEILO > is displayed to indicate that CL31 is ready for command
input from the user. The commands are executed by pressing ENTER,
for example,
OPEN 1 <enter>. No automatic transmission of the
measurement data message is executed in the open state. The port
reverts to the closed state with the
close command. An automatic, 2-
minute time-out after the last character input is applied. A 2 to 30-
minute time-out may be set with the
set port_timeout command.
NOTE
Only one of the ports can be open for commands at a time. Only one of
the ports transmits measurement messages at a time. Additionally, in the
RS-485 mode, a unit ID must be given with the
open command.