Controlling Protocol ......
“Write to the Rx N
OTONE
Timer Register”
– A/C 33
H
followed by 1 byte of Command Data.
Setting
MSB
7 6
0
0
3
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
Function/Period
Operation of the Rx N
OTONE
Timer
4
0
0
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
5
0
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
Transmitted Bit 7 First
These 4 bits must be “0”
High/Extended
Band
period (ms)
0
"
20
±1%
40 "
60 "
80 "
100 "
120 "
140 "
160 "
180 "
200 "
220 "
240 "
260 "
280 "
300 "
Mid
Band
0
40
±1%
80 "
120 "
160 "
200 "
240 "
280 "
320 "
360 "
400 "
440 "
480 "
520 "
560 "
600 "
2
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
An Rx N
OTONE
period is that period when no signal or a
consistently bad-quality signal is received.
The Rx N
OTONE
Timer can be employed to indicate to the
µController
that a N
OTONE
situation has existed for a
predetermined period.
This timer register can be written-to and set in any
mode of the FX803.
The N
OTONE
Timer period is ‘primed’ by writing to the
N
OTONE
Timer Register (33
H
) using the settings given in
Table 6.
“Priming” sets the timing period;
this period can only
start directly after a frequency (tone) measurement
has been successfully completed.
The N
OTONE
Timer is a one-shot timer being reset only
by successful tone measurements.
If the quality of the received signal drops to an unusable
level the N
OTONE
Timer will start its run-down.
On completion of the preset period, the N
OTON
e Timer
Period Expired bit in the Status Register and the Interrupt
(when enabled,
Table 2
) are set.
Upon detection of the Interrupt, the Status Register
should be read by the
µController
to ascertain the source
of the Interrupt.
The N
OTON
e Timer Period Expired bit is cleared:
i
By a read of the Status Register or,
ii New N
OTONE
Timer information or,
iii General Reset command
This timer is set to 00
H
(0ms) by a General Reset command.
Table 6 Rx N
OTONE
Timer Settings
The following situations may be encountered by the N
OTONE
Timer circuitry:
No Signal
The N
OTONE
Timer can only start its run down on
completion of a valid frequency measurement.
Signal Fades after a Valid Tone Measurement
The timer will start to run down when the signal becomes
unreadable to the device. At the end of the “primed” period
the N
OTON
e Timer Period Expired bit in the Status Register
and the Interrupt will be set.
No Signal after a Valid Tone Measurement
The timer will start to run down when the last Rx Tone
Measurement complete bit is set. At the end of the
“primed” period the N
OTON
e Timer Period Expired bit in the
Status Register and the Interrupt will be set.
Signal Appears after the Timer has Started
If the frequency measurement is more than 75% complete
when the timer period expires, neither the N
OTONE
bit nor
the Interrupt will be set unless that frequency
measurement is subsequently aborted.
10
CMLMICRO [ CML MICROCIRCUITS ]
