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
established 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 inputs,
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'
good
'3' and '5'
bad
