Appendices
Bushealth Measurements
A
A-11
RS-232 Bus.
RS-232 allows two-way communication between a
controller and a device such as modem, printer, or
sensor. Per device a dedicated link is needed. Initially the
RS-232 definition offered an extensive handshake
protocol with separate handshake lines (hardware
handshake); later software handshake allowed data
exchange via only 2 lines (plus ground). Data rates may
be low, depending on the application.
To check this bustype, ScopeMeter Channel A is on and
DC coupled. The recommended probe is the Fluke 10:1
probe. Connect the probe as shown below.
x
or
x
GND
In case there are handshake lines, they each can be
checked individually because all use the same voltage
levels.
The figure below shows a Female DB-9 connector wired
for hardware handshake. Lines used for software
handshake are indicated with black dots.
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