Rs-232 (Ccitt V.24); Rts - Omega DP41-B Series User Manual

4. Definitions

4.8 RS-232 (CCITT V.24)

Bipolar ±5 to ±15 V point-to-point transmission for short distances and moderate data
rates. The meter operates with full-duplex RS-232, with two wires (RX and TX), plus a
common ground, to transmit baud in either direction. A third signal wire, Request To
Send, is referenced to the same ground wire and is used by the computer (DTE) to
control transmissions of the meter (DCE).
Receiver sensitivity is ±3 V and impedance of 3 to 7 kilohms. (Although RS-232 is
nominally for only one driver and one receiver on the line, custom high-impedance
versions exist for limited multipoint use.)

4.9 RTS

A designator for the "Request To Send" control signal from the computer, carried on a
wire separate from that of the data, and used by the meter to permit or inhibit
transmissions in Continuous Mode RS-232. The other control line of RS-232, CTS, is
not used in meter communications.
4.10 RS-422
Unipolar-voltage (3.6 to 6 V supplies) simplex drive of a bus with ±2 V-differential
signals (neither wire at ground) for long distances and/or high data rates. Receiver
sensitivity 200 mV, common-mode voltage range ±3 V, and impedance 4 kilohms or
more. A maximum of one driver and 10 receivers allowed, with no driver protection
against bus contention. Duplex operation requires another set of hardware.
4.11 RS-485
This is the extension of RS-422 to a half or full duplex bus of up to 32 devices, with
multiple drivers and driver-contention protection. Receiver impedance is now
12 kilohms or more.
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