SI3201-X-FS View Datasheet(PDF) - Silicon Laboratories

Part Name

Description

Manufacturer

SI3201-X-FS

PROSLIC® PROGRAMMABLE CMOS SLIC WITH RINGING/BATTERY VOLTAGE GENERATION

Silicon Laboratories 

Si3233

2.4.2. Oscillator Frequency and Amplitude

Each of the two tone generators contains a two-pole

resonant oscillator circuit with a programmable

frequency and amplitude, which are programmed via

indirect registers OSC1, OSC1X, OSC1Y, OSC2,

OSC2X, and OSC2Y. The sample rate for the two

oscillators is 16 kHz. The equations are as follows:

coeffn = cos(2π fn/16 kHz),

where fn is the frequency to be generated;

OSCn = coeffn x (215);

OSCnX = -14- ×

-1-----–----c---o----e----f--f

1 + coeff

×

(

215

–

1

)

×

D-----e----s---i--r--e----d------V----r--m----s-

1.11 Vrms

where desired Vrms is the amplitude to be generated;

OSCnY = 0,

n = 1 or 2 for oscillator 1 or oscillator 2, respectively.

For example, in order to generate a DTMF digit of 8, the

two required tones are 852 Hz and 1336 Hz. Assuming

the generation of half-scale values (ignoring twist) is

desired, the following values are calculated:

coeff1

=

cos

⎛

⎝

2-1---6π---0-8---05---0-2-⎠⎞

=

0.94455

OSC1 = 0.94455(215) = 30951= 78E6h

OSC1X = 14-- ×

-0----.-0----5---5---4----5-- × (215 – 1) × 0.5 = 692 = 2B3h

1094455

OSC1Y = 0

coeff2

=

cos

⎛

⎝

2--1--π--6--1-0--3-0--3--0--6--⎠⎞

=

0.86550

OSC2 = 0.86550 (215) = 28361 = 3EC8h

OSC2X

=

-1-

4

×

0----.-1----3---4----5---0-- × (215 – 1) × 0.5 = 1098 = 44Bh

1.86550

OSC2Y = 0

The computed values above would be written to the

corresponding registers to initialize the oscillators. Once

the oscillators are initialized, the oscillator control

registers can be accessed to enable the oscillators and

direct their outputs.

2.4.3. Tone Generator Cadence Programming

Each of the two tone generators contains two timers,

one for setting the active period and one for setting the

inactive period. The oscillator signal is generated during

the active period and suspended during the inactive

period. Both the active and inactive periods can be

programmed from 0 to 8 seconds in 125 µs steps. The

active period time interval is set using OAT1 (direct

registers 36 and 37) for tone generator 1 and OAT2

(direct registers 40 and 41) for tone generator 2.

To enable automatic cadence for tone generator 1,

define the OAT1 and OIT1 registers and then set the

O1TAE bit (direct Register 32, bit 4) and O1TIE bit

(direct Register 32, bit 3). This enables each of the

timers to control the state of the Oscillator Enable bit,

O1E (direct Register 32, bit 2). The 16-bit counter will

begin counting until the active timer expires, at which

time the 16-bit counter will reset to zero and begin

counting until the inactive timer expires. The cadence

continues until the user clears the O1TAE and O1TIE

control bits. The zero crossing detect feature can be

implemented by setting the OZ1 bit (direct Register 32,

bit 5). This ensures that each oscillator pulse ends

without a dc component. The timing diagram in

Figure 12 is an example of an output cadence using the

zero crossing feature.

One-shot oscillation can be achieved by enabling O1E

and O1TAE. Direct control over the cadence can be

achieved by controlling the O1E bit (direct Register 32,

bit 2) directly if O1TAE and O1TIE are disabled.

The operation of tone generator 2 is identical to that of

tone generator 1 using its respective control registers.

Note: Tone Generator 2 should not be enabled simulta-

neously with the ringing oscillator due to resource shar-

ing within the hardware.

Continuous phase frequency-shift keying (FSK)

waveforms may be created using tone generator 1 (not

available on tone generator 2) by setting the REL bit

(direct Register 32, bit 6), which enables reloading of

the OSC1, OSC1X, and OSC1Y registers at the

expiration of the active timer (OAT1).

Preliminary Rev. 0.5

27

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