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Connect Tech Blue Heat/Net Sync User Manual
72 Revision 0.03
Figure 32: Typical Asynchronous Date Frame
Serial Line Interface Tutorial
RS-232 Line Interface:
RS-232 is the simplest, least expensive line interface standard, the Sipex tranceivers used on the
Blue Heat/Net Sync refer to RS232 as V.28 mode. It is also referred to as EIA232 and TIA/EIA-
232. The RS-232 specification signals levels of +3V to +15V for a logic 0 or Space, and -3V to -
15V for a logic 1 or Mark. The Blue Heat/Net Sync has RS-232 signal levels with a typical
range of +/- 8 Volts. The maximum cable length you can use with RS-232 is dependant on a
number of factors including:
Baud rate: The higher the baud rate, the shorter the cable length must be.
Cable quality: Quality largely refers to the capacitance of the cable. A higher capacitance
(usually specified as pF or pico Farads per foot) dictates a lower baud rate, and a shorter
maximum length. Low capacitance computer cables for RS-232 applications are available from
all wire and cable suppliers.
You can usually operate with cable lengths of up to 100 feet (30 m) at baud rates up to 115.2
Kbps using low capacitance cable. For higher baud rates such as 230.4 Kbps and up, we
recommend keeping the cable lengths to within 25 feet (7.6 m).
The TIA/EIA232 specification specifies two connectors: the DB-25 and the DB-9. Each of these
connectors has a standardized pinout. Refer to the Pinouts section of the manual for the DB-25
RS-232 (V28) pinout.
Differential Line Interfaces:
The Blue Heat/Net Sync features Sipex SP508 multi-protocol transceivers. These transceivers
features the following differential line standards.
V.11: A differential line interface with signal levels compatible with RS-485 and RS-422.
V.10: A single ended line interface that can be wired such that it will have some of the noise
cancelling features of RS485 (V.11). This interface is also called RS-423.
V.35: A differential line interface that operates in a current loop. The electrical levels are about
+/- 550mV.
RS485/RS422/V.11 Details
V.11, RS-485, or TIA/EIA485, is a differential line interface standard capable of high baud rates
over long cables. The Sipex tranceivers used on the Blue Heat/Net Sync refer to RS-485 as V.11