ICS ELECTRONICS 4809A, Instruction Manual

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A-21
A2
A2.4 RS-530 Pinouts
In 1987, the EIA released a new standard, EIA-530, for high speed signals
on a 25 pin connector. This new standard combined the older RS-232
single-ended signals and the newer RS-422/RS-485 differential signals on
one connector. The advantage of the RS-530 specification is that it estab-
lished a pin out standard for RS-422/RS-485 signals on a 25 pin connector
and at the same time provided for the presence of both signals on the same
connector.
The 2303 serial interface conforms to the EIA-530 Standard and uses internal
jumpers to select the active signal levels on its serial interface. The 2303 is
designed so that it may receive either single ended RS-232 or differential
RS-422/RS-485 signals.
A2.5 Serial Interface Problems
Most of the problems that arise when connecting serial devices can be
avoided if the user will compare the signals on both devices' interfaces
before plugging them together. The obvious things to look for are:
1. Verify transmit and receive data direction and pin numbers.
DTE devices mate directly with DCE devices while DTE
and DTE connections need to be crossed.
2. Check needed control lines. Some devices need signal in-
puts, others can function with open inputs. All inputs need
a valid signal level. If in doubt add jumpers to a known 'on'
signal such as the devices's DTR or DSR output signal.
3. Same baud rates. Different baud rates result in garbled
data.
i.e., *!1-
4. Same character formats. It may be obvious but often the
character formats and parity settings are incorrect. A typical
parity setting symptom is half good-half bad characters.
i.e., '1', '2', '4' 3 and 5 missing
'3','5' 1, 2 and 4 missing