1892 1139 - RSX Range of Intelligent Modems User Guide - v7.1 / Nov 2007
9
1.
When the modem buffer is full
2.
When there is a signal on-channel (indicated by the squelch being active high) and
transmission cannot therefore take place. When the TX squelch override is
enabled, transmission is permitted, and CTS remains high.
If the input data rate is less than the over-air data rate and there is therefore no danger of
buffer overrun, and transmission will never be inhibited by the squelch because the TX
squelch override is enabled, the CTS output can be left disconnected and the
corresponding input at the customer equipment can be wired high.
v
A true connection to the PC is essential when programming the modem using the
WinSetGMSK software.
This table summarises the RSX
n
50 CTS output state under various circumstances:
Normal Operation
Programming
modem with
WinSetGMSK
Programming
radio
TX Buffer state
Full
Not full
N/A
N/A
Squelch state
Don’t care
Inactive
Active
N/A
N/A
TX Squelch
Override
Don’t care
Don’t care
Disabled
Enabled
N/A
N/A
CTS output
Low
High
Low
High
Used by software
N/A
1.2.3.3
PGM
This input is used solely for radio programming, and has no function during normal use. It
should be left open-circuit, as any spurious signals applied could cause the SX
n
50
transceiver to become incorrectly programmed, indicated by the orange LED lighting or a
logic low on the LED output (OEM version with IDC connector only).
1.2.3.4
RS232 Levels
The RSX
n
50 provides a bipolar output of
+
10V on RS232 lines which should be
acceptable to the vast majority of RS232 interfaces. These levels have the conventional
significance, as follows:
Voltage
Name
Logic level
Assertion (RTS etc)
Bit value (data)
+10V
Space
High
True
0
-10V
Mark
Low
False
1
It will also accept non-RS232 level inputs as supplied by some PCs, where
high is b2V and +supply
and
low is between -supply and 0V.
