Specifications

Appendix G
RTS Operation
The D1000R/2000R series analog input modules interface to radio and
leased telephone line modems. Many of these modems require an RS-232
signal to activate, or “key-up”, the transmitter. They also require adequate
delay time for the transmitter to turn on before transmitting data. The amount
of delay time required varies between modem types and manufacturers.
Typical time periods range from 150ms for leased line modems to 500ms for
radio modems.
D1000/2000 modules have a quick response turnaround time. After a
module receives a valid command, it takes typically 10ms (RD command)
for a module to begin transmitting data. This response time is much too fast
for the transmitter delays associated with radio frequency and leased-line
modems. The R series is designed to solve this problem.
The D1000R/2000R series modules each contain a Request-To-Send
(RTS) output to synchronize RS-232 data to radio frequency or leased-line
modems. The RTS signal is used as a hand-shaking signal to activate and
deactivate a modem transmitter. Once the transmitter turns on, it is safe to
transmit the data. The RTS signal normally remains on until immediately
after the last data character is transmitted.
The D1000R/2000R series modules are designed for applications that
contain one analog process point per modem. For applications containing
multiple analog points per modem the A2400 Radio Modem Interface is
recommended. The A2400 converts RS-232 modem data to RS-485 and
provides RS-232 handshaking signals to the modem. The A2400 is used
with standard D1000R/2000R series RS-485 modules.
The D1000R/2000R series is similar to the standard D1000/2000 series.
This manual is an appendix to the D1000 series manual. Users of the
D1000R/2000R RTS modules should read the D1000 series manual. The
commands listed below are additional commands found only in the D1000R/
2000R series.
THEORY OF OPERATION
The D1000R/2000R series analog input modules each contain an RS-232
Request-To-Send (RTS) output signal. The RTS signal may be activated
using simple ASCII commands. The RTS output signal works together with
three user programmable time delays that control the operation of the RTS
signal. Each delay has a user-programmable range of 0 to 2000ms and may
be set to 1ms resolution. The delay values are stored in EEPROM and must