Specifications

Appendix F
D1000/2000 Continuous Operation
All D1000/2000 computer interface modules may be factory-configured to
provide continuous output of analog input data. A D1000/2000 continuous
module is intended for applications where no host computer is present. The
limitation to the continuous mode is that only one module can be on the
communications line.
Continuous output may be ordered by adding a “C” suffix to the model
number. For example, a D1111 with the continuous output option may be
ordered by specifying model number D1111C.
Interfaces with the “C” option have one connector pin labeled CONT*. This
input pin is used to activate the continuous mode. The “*” in CONT* label
indicates that the signal is active low. The CONT* signal is pulled up
internally in the module and is voltage protected up to ±30Vdc.
If the CONT* line is left open or pulled high (>3.5Vdc), the module will
operate normally as described in the manual. The only change is that the
CONT* input occupies a pin normally used for a digital input or output.
If the CONT* input is pulled low or shorted to GND, the module will
continuously output the analog input data. The data output is transmitted in
the “short form” response format. For example, a typical output would look
like *+00100.00. Each data message starts with an asterisk (*) and is
terminated with a carriage return. Communication delays and line feeds may
be added if necessary using the Set Up Command (see manual).
When the CONT* input is held low, the module will not respond to any input
commands. Usually this is not a problem since in most cases a continuous-
output module is used in a dedicated output-only application. If it is
necessary to send commands to the module, some means of switching the
CONT* line must be employed. This may be in the form of a simple toggle
switch between the CONT* line and GND. The switch may be located local
to the module or a dedicated wire may be run from the module to the host.
If a module with RS-232 communications is used with a host computer, the
continuous mode may be controlled by running a wire from the CONT* pin
to an RS-232 control signal, such as Request To Send (RTS). The RTS
signal may be turned on and off by the computer to select continuous or
normal mode. The CONT* input will handle the RS-232 voltage levels since
it is protected to ±30Vdc.