Owner`s manual
Page A-3Serial, Parallel, UPS and Ethernet Connector Configurations
Although printer cables are sometimes a little more complicated on the printer end,
terminal cables are often the same on both computer and terminal ends.
Alpha Micro uses both the DB-25 pin connector and the DB-9 pin connector for RS-232
device connection. Your computer may use DB-9 or RJ-45 connectors at the computer
end, depending upon model numbers. The maximum length of RS-232 cables is 50
feet between devices.
WHAT IS RS-422?
RS-422 is supported by the AM-314 board only. Because of rapid technological
advancements, it became necessary to extend the RS-232 standard. The EIA
adopted three related standards that permit higher data signaling rates, greater
distances between devices, balanced interface circuits, and loop-back testing. The
standards are RS-422, RS-423 and RS-449. For Alpha Micro computers, we need be
concerned with only RS-422 and RS-232. Longer cables are allowed if the user uses
low capacitance twisted paired cable. This cable should have an overall shield which is
grounded. This is necessary to eliminate EMI (ElectroMagneticInterferance) from
affecting the communications link between the device and the computer. This shielded
cable also eliminates emitted electrical interfence to other systems. Cable length and
type will be explained in a later section.
The RS-422 interface uses balanced signal lines in pairs. It has greater immunity to
electrical noise and can run over longer cables. The maximum length of Alpha Micro
RS-422 cables is 1000 feet. The user should install data line voltage protection on
cables that are from 200-1000 feet long. The maximum data rate for both RS-232 and
RS-422 signals is 57.6K.
All AM-314 serial I/O ports can be configured for RS-422 operation. In addition, your
serial peripherals must be able to operate using RS-422 signal levels.
The AM-318 serial I/O board, as well as the Eagle 100’s eight on-board serial ports, and
the Eagle 550’s four on-board serial ports do NOT support RS-422.
IMPORTANT NOTE:
The Federal Communications Commission (FCC) has established rules regarding
allowable emission levels of Class A computing devices (ref: Subpart J of Part 15 of
FCC Rules). The Alpha Micro systems to which this manual applies have been
determined to be in compliance with the FCC rules. However, you should be aware that
if other devices, such as terminals and printers, are attached to these systems, even if
the devices are attached in accordance with the instructions contained in this manual,
the resulting configuration may not be in compliance with the referenced FCC rules.
Corrective measures, if any are required, are the responsibility of the user. Information
on emission levels of peripheral devices should be obtained from the manufacturer of
the device.
Eagle Series Computer Owner’s Manual, Rev. 03