Tone Operations
Tone Detection
SIGNAL IN
Decoder Input
Level Setting
FREQUENCY
ASSESSMENT AND
MEASUREMENT
DIGITAL FILTER
When the CMX823 detects the start of a valid
in-band tone (a tone in the selected user-
defined tone list) it generates an interrupt and
V
DD
/2
reports, via its on-chip C-BUS interface, which
tone was detected. At the end of that tone it
OPAMP OUT
produces another interrupt and reports N
OTONE
detected. This information is available, in
several forms, to enable the host µC to measure and interpret the tone and gap
lengths according to the toneset requirements. These actions take place for each
response/de-response action no matter what the length of the tone sequence.
SERIAL CLOCK
SEQUENCER
AND
COMPARATOR
C-BUS
INTERFACE
AND
CONTROL
LOGIC
CSN
IRQN
COMMAND DATA
REPLY DATA
Tone Parameters
Load Tone Parameters
Tone parameters are stored in one or both of the ‘tone lists’. The tone decode
parameters for the selected list and group are sequentially retrieved and matched
with those of the received signal to find a tone decode. Tone decode status
changes are flagged in the Status Register.
Tone List 1
Location
0
1
2
3
.
.
.
30
31
Tone Group
1
2
Tone Parameters
Location
0
1
2
3
.
.
.
30
31
Tone List 2
Tone Group
1
2
Tone Parameters
The parameters for decoding each tone in the tone list are stored separately.
Two selectable lists are available; only one is accessed at any one time. List
contents are preloaded by the host and are maintained during ‘table-switching’
and ‘Zero-Power’ mode powersave operations.
Tone decode parameters can be designated, within a tone list, to either one or
both tone-groups; these groups can be used to represent the first or second
tones in a tone sequence.
Upon reception and measurement of an input tone, the tone decode parameters
of the selected group are sequentially retrieved from the selected list and
compared with the decoded parameters. A match will result in the generation of
an interrupt and the decoded tone’s status and parameters.
Decoded Tone Location
Register
Tone Position
in Selected List
Decoded Tone Parameters
Register
Tone Group
Tone Parameters
(as loaded)
Status
Register
Tone Change
Decode Status Change
Tone Decode
Unlisted Tone
tone and decode
indications and
parameters available
to the host µC
Tone Lists, Indications and Parameters
Decode Tone Bandwidths
These bandwidth settings, variable between ±0.1% to ±3.1%, are available for compliance to all
radio signalling and toneset specifications. These settings can be also used to ‘tune’ the decode
process by preventing false decoding due to ‘bandwidth overlap’ and to enable the accurate
reception of unstable Rx signals.
Tone Lists and Groups
The CMX823 contains two ‘tone lists’ (1 and 2) each capable of storing parameters for thirty-two
user-designated tones. Each list can be further sub-divided into two ‘tone groups’. Each ‘tone list’
is intended for use with a single RF channel allowing a fast list-switch (between 1 and 2) when
changing RF channels.
Tone decode parameters can belong to either or both ‘tone groups’; a feature which may be used
to represent the first and second tones in a tone sequence; this will further speed-up the decoding
process.
Decode Reporting
To enable further efficiency and speed in tone decode reporting to the host, the Status Register
indicates, separately, the various decode actions.
Tone Change:
Unlisted Tone:
N
OTONE
:
Tone List:
Whenever a ‘listed’ tone-decode changes
The decoding of any tone in the valid frequency range but not in the
selected list.
The loss of a valid tone. An automatic N
OTONE
timer period is instigated.
The list that was selected when the match was found.
Fast and Slow Measurement Modes
These two modes of response/de-response time measurement are available to allow the most
efficient use of µC time and to facilitate the widest range of paging tone-set format requirements.
Fast mode is intended for 5/6-tone paging tonesets and Slow mode for 2-tone paging tonesets
where slower response times are acceptable. For bespoke systems, these modes can be
employed for the reduction of false decodes.
Decode Status Change:
Any change in the decoder operation
CMLMICRO [ CML MICROCIRCUITS ]
