Commercial In Confidence
39
corrupted (failed checksum) in the general program area.
7
Internal comms with a high power amplifier have failed.
8
The contents of the microprocessor's EEPROM are
corrupted (failed checksum) in the calibration area.
9
The contents of the microprocessor's EEPROM are
corrupted (failed checksum) in the factory program area.
12
The programmed R.F. power setting is out of range.
3.18 TIME-OUT-TIMER
The time-out timer allows the maximum continuous transmission time to be set in order to
prevent channel blocking due to a host fault. The timer works in all modes (external/internal
modem) and is programmable in one second steps between 0 and 255 seconds. In all cases
transmission will cease until the action that normally causes transmission is removed and
then re-applied. More explicitly; in external modem mode the transmit enable line (DI0) must
be released and then lowered again, in internal modem modes with RTC/CTS handshake
enabled RTS must be dropped and then raised again, or if handshake is not enabled character
transmission must be suspended for at least two character periods at the serial port baud rate.
In all modes the modem’s SYS led is flashed at least twice when time-out occurs, the flashing
continues while lockout is in force. The lockout timer is disabled if the lockout time is set to
0. The lockout timer can be operated in “resettable” or “cumulative” mode, in resettable
mode the timer restarts each time a transmission is made, in cumulative mode the timer
counts up during transmit, and down during receive. If the timer counts up to the lockout
time during transmit lockout occurs, this will eventually happen if the radio spends more
than half of its time transmitting. Lockout in this mode is indefinite and can only be reset by
powering the radio off.
3.19
POWER SAVE MODE:
The ART is equipped with an internal and external power save mode
. T
hese are outlined
below:
1. The internal power save facility: In this mode the microprocessor switches the transceiver
off and after a pre-programmed time (Save on time) switches the unit back on (Save off time).
If a carrier is not detected then the transceiver again switches off. If during the time the
transceiver is awake a carrier is received, the unit will stay on. After the carrier drops out the
receiver will stay on until the programmed resume time elapses. Once the resume time has
elapsed the unit will return to its power save mode. The Save On/Off and Resume time are
all programmable via the PC program. Obviously the amount of power saved increases with
the programmed save on/off ratio, however with power save enabled long lead times must
be programmed to wake up the unit before communication can take place. Therefore it may
not be possible to run all applications under the power save mode due to the turn around
times required by the host system. In some circumstances it is possible to achieve power save
and fast polling: If polling of all outstations is carried out in cycles with a reasonable gap
between each cycle, a long initial poll can be used to wake up all stations, the resume timer
will then restart each time an outstation is polled allowing fast access, when the cycle is
complete all stations will return to power save after the resume time has expired.
2. The External power save mode: Under this mode the on/off ratio is controlled externally
via the DTR line (DTR shut down must first be enabled using the set up program). In this
mode more of the modem's circuits are shutdown (including the microprocessor), this saves
more power but care must be taken to ensure that the modem is enabled when a transmission
is to take place. Note that there is a hardware link option to allow the serial port to shut off