Table of Contents
Advertisement
Settings
Commands to set automatic transmitter switch off
< s e t i n t e r f a c e f s k 0 a u t o - o f f { 0 - 1 0 0 s | a u t o } >
The carrier and therefore monitoring too are switched off if RTS=OFF within the time window.
However, if the DTE does not switch RTS=OFF within this time, the modem will switch off the
carrier. This function ensures that, if DTE and multi-drop communication are faulty, the transmission
cannot be blocked by a "permanent transmitter".
2.9.11
Quality check
The 500FSD20 modem allows the received signal to be monitored for excessive isochronous
distortion during operation. If a threshold value is exceeded, the modem indicates this via the LED
SQL (SQL= signal quality level) and activates the alarm relay if it is configured.
The threshold value is set at 40% for bit rates from 50 to 1200 bps, and 50% for a bit rate of
2400 bps. If the received signal exceeds this value at least ten times in intervals of less than four
seconds in each case, the LED SQL will be switched ON and the alarm relay will be activated. If
the interval between two instances of the value being exceeded is greater than four seconds, the
relay resets again, the LED SQL is switched OFF and the internal counter is reset. If additionally
the evaluation of signal quality is switched on by the command < s e t i n t e r f a c e f s k 0 s q -
e v a l u a t i o n > , no more receive data will be output on RxD after exceeding the threshold value.
Commands to activate or deactivate the SQL quality check and the sq-alarm
< s e t i n t e r f a c e f s k 0 [ n o ] s q - e v a l u a t i o n >
< s e t i n t e r f a c e f s k 0 [ n o ] a l a r m s q >
2.9.12
DCD alarm (carrier monitoring)
The DCD signal indicates that the modem has detected a carrier on the receive channel. If this is
the case, it will switch on the LED DCD without delay, or switch it off if there is no carrier.
In half-duplex mode, the transmitter on the opposite side is activated periodically. The length of
these gaps is determined by the bit rate and the telegram length of the response. The modem takes
account of this and reports that a carrier is missing via the alarm relay with a delay. The delay is
determined by the command < s e t i n t e r f a c e f s k 0 a l a r m d e l a y { 0 - 6 0 0 s |
a u t o } > . The setting auto sets the delay dependent on the bit rate. Alternatively a delay between
0 and 600 s can be selected: only if DCD is absent for at least n seconds the alarm relay drops out.
At the same time, the LED SQL switches on. The status is therefore indicated by the LEDs.
Carrier missing:
• LED DCD = OFF
• LED SQL = ON
Depending on the bit rate, the drop-out time is:
• 50 bps - 16 s
• 100 bps - 8 s
• 200 bps - 4 s
• 600-2400 bps - 2 s
Commands to set the alarm delay
< s e t i n t e r f a c e f s k 0 a l a r m d e l a y { 0 - 6 0 0 s | a u t o } >
28
Functions
1KGT151043 V001 1
Advertisement
Table of Contents
