RS-485
RS-485 is backwardly compatible with RS-422; however, it is optimized for
partyline or multi-drop applications. The output of the RS-422/485 driver is capable
of being Active (enabled) or Tri-State (disabled). This capability allows multiple
ports to be connected in a multi-drop bus and selectively polled. RS-485 allows
cable lengths up to 4000 feet and data rates up to 10 Megabits per second. The signal
levels for RS-485 are the same as those defined by RS-422. RS-485 has electrical
characteristics that allow for 32 drivers and 32 receivers to be connected to one line.
This interface is ideal for multi-drop or network environments. RS-485 tri-state
driver (not dual-state) will allow the electrical presence of the driver to be removed
from the line. Only one driver may be active at a time and the other driver(s) must
be tri-stated. RS-485 can be cabled in two ways, two wire and four wire mode. Two
wire mode does not allow for full duplex communication, and requires that data be
transferred in only one direction at a time. For half-duplex operation, the two
transmit pins should be connected to the two receive pins (Tx+ to Rx+ and Tx- to
Rx-). Four wire mode allows full duplex data transfers. RS-485 does not define a
connector pin-out or a set of modem control signals. RS-485 does not define a
physical connector.
RS-530 / 530A
RS-530 (a.k.a. EIA-530) compatibility means that RS-422 signal levels are met, and
the pin-out for the DB-25 connector is specified. The EIA (Electronic Industry
Association) created the RS-530 specification to detail the pin-out, and define a full
set of modem control signals that can be used for regulating flow control and line
status. The major difference between RS-530 and RS-530A lies in some of the
modem control interface signals. In RS-530 the signals all of the modem control
signals are differential, in RS-530A some of these signals are single ended. The
RS-530 specification defines two types of interface circuits, Data Terminal
Equipment (DTE) and Data Circuit-Terminating Equipment (DCE). The Sealevel
Systems adapter is a DTE interface.
V.35
V.35 is a standard defined by ITU (formerly CCITT) that specifies an electrical,
mechanical, and physical interface that is used extensively by high-speed digital
carriers such as AT&T Dataphone Digital Service (DDS). ITU V.35 is an
international standard that is often refereed to as Data Transmission at 48 Kbps
Using 60 - 108 KHz Group-Band Circuits. ITU V.35 electrical characteristics are a
combination of unbalanced voltage and balanced current mode signals. Data and
clock signals are balanced current mode circuits. These circuits typically have
voltage levels from 0.5 Volts to -0.5 Volts (1 Volt differential). The modem control
signals are unbalanced signals and are compatible with RS-232. The physical
connector is a 34 pin connector that supports 24 data, clock and control signals. The
physical connector is defined in the ISO-2593 standard. ITU V.35 specification
defines two type of interface circuits, Data Terminal Equipment (DTE) and Data
Circuit-Terminating Equipment (DCE). The Sealevel Systems adapter is a DTE
interface.
© Sealevel Systems, Inc.
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ACB-MP+4.PCI User Manual
