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PDF SA9401 Data sheet ( Hoja de datos )
| Número de pieza | SA9401 | |
| Descripción | UNIVERSAL PABX TONE GENERATOR | |
| Fabricantes | Sames | |
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SA9401
UNIVERSAL PABX TONE GENERATOR
FEATURES
s Generates PBX supervisory tones in s Each of these tone streams selectable
PCM format
from 16 tone blocks
s Integrated time slot allocation circuitry s Seperate Intrude Tone for each pro-
s No noticeable level changes in tones
gram
s Choice of clock frequencies
s Frame synch. signal source (internal/
external) selectable
s Watchdog facility
s Eight tone programs
s Low power CMOS technology
s Eight independent PCM tone streams
within each program
PROGRAMMABLE FEATURES
s Tone samples
s Tone Cadence timing
s Tone to time-slot mapping
s Size of tone blocks
s Intrude tone frequency
s Intrude tone cadence
s "silence sample" value
DESCRIPTION
The SA9401 operates in conjunction with a standard EPROM to generate the system
tone plans for the PABX systems of most major countries.
The high level of programmability allows the SA9401 to satisfy a wide variety of tone
plans. Furthermore by providing three inputs to select between one of eight tone
programs during initialisation, the device effectively facilitates the design of a universally
programmable "PABX Processor Card". Because the tone program inputs are latched
at the start of each PCM frame the SA9401 minimises the possibility of glitches.
The SA9401 can also generate the PCM Frame synchronising reference signal if
required.
4092
PDS039-SA9401-001
REV. C
07-05-96
1 page  
SA9401
Intrude Tone Generator
This module generates a square wave output based on the master clock of 2048kHz.
The Intrude Tone frequency is determined by the contents of the 16-bit Intrude Tone
Register (INTR_LO and INTR_HI) according to the formula:-
f = 2048kHz/(2*(n+1))
int
where n is the content of the INTR register.
The range of values in the register (from 0 to 65535) give Intrude tones in the range
15.625Hz to 1024kHz.
Cadence Timer
In any given Tone Plan the SA9401 assumes that any or all of the 9 (8 PCM tone
streams and one squarewave Intrude Tone) tones are required to have their own inde-
pendently defined cadence. A typical cadence is illustrated in FIGURE 1 above. Each
tone is assumed to comprise up to 4 cadence periods which repeat cyclically. The
duration of each period is controlled by the Cadence Timers which in turn comprise 10-
bit Counters. These timers are clocked by the five_ms_timebase generated by the
Clock Generator so that intervals of up to 5.12 seconds can be defined with a resolution
of 5ms. (10 bits => 1023: 1023*5ms = 5115ms)
ON OFF ON
OFF
TONE_n_A
TONE_n_B
CADO_n
CAD1_n
CAD2_n
CAD3_n
DR-01086
FIGURE 1: TONE CADENCING
The Cadence Controller controls the loading of the 10-bit counter and the sequencing
of the Cadence Position Counter. The duration of each period of the tone is denoted by
the parameter:-
CADm_n_LO = Period m, Tone stream n low-order 8 bits and
CADm_n_HI = Period m, Tone stream n high-order 2 bits
where 0 ≤ m ≤ 3 and 0 ≤ n ≤ 8 (8 = Intrude Tone)
The Cadence Position Counter keeps track of the period being generated and during
period 0 the SA9401 generates a tone based on one Tone Block (A) while during the
period 2 (if used) the samples from another Block (B) are used. During periods 1 and 3
the silence sample is transmitted. This feature allows the sound of the tone to be
altered along with the cadence.
A continuous tone is created by loading values of 1(or any non-zero value),0,0,0 into
the registers CAD0_n to CAD3_n respectively. The zero value is interpreted by the
SA9401 as an instruction to ignore the period and to process the next one. With the
register contents shown the Cadence Controller continuously processes the first (ON)
period.
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5
5 Page 
SA9401
Tone Waveform
The frequency content of any desired tone is defined by taking one cycle of the tone
(which may be a simple or complex waveform) and calculating the series of PCM sam-
ples which would result if that tone were passed through a CODEC. The definition of a
waveform is perhaps best illustrated by way of an example.
Consider the case of a PTT dial tone which is a signal of 400Hz modulated at 33.33Hz
as illustrated in fig. 4 below. The first step is to identify the lowest frequency in the
composite signal, in this case 33.33Hz. Next the designer should confirm that one
cycle of the lower frequency component of the signal will contain an integer number of
cycles of the higher frequency component. In the example there are exactly 12 cycles
of the 400Hz signal contained within the one cycle of the modulating signal. If this is
not the case then the tone sample should be designed to contain two or more cycles of
the lower frequency tone, subject to the maximum of 512 samples. It is also typical to
take a block of the signal which starts and ends at two similar zero crossing points.
Although any arbitrary point in the waveform may be used a careless choice may lead
to the introduction of undesirable harmonics.
Having chosen a suitable tone sample it is possible to determine the value for CYCLE
as the size of the tone block is simply the number of samples (at 8k samples per
second) which fall into the waveform chosen. In the example CYCLE = 240 samples =
F0H.
1 / 33.3Hz = 30ms
FIGURE 4
1 / 400Hz = 2.5ms
30ms @ 8k SAMPLES / sec = 240 SAMPLES = CYCLE
400Hz Tone modulated at 33.33Hz.
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11
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| PDF Descargar | [ Datasheet SA9401.PDF ] | |
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