MFC2000 datasheet(364/426 Pages) ETC

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MFC2000 Multifunctional Peripheral Controller 2000

Hardware Description

20-6

Conexant

100723A

20.3 Tone Generator

There are two tone generators which can be operated independently, namely ALTTone and Tone. ALTTone can

be used alone or with the bell/ringer generator for modulation purpose. The duty cycle of the tone signal is 50%.

Frequency modulation on the tone signal can be controlled by the firmware. While the tone generator is running,

the firmware may write a new value to the frequency register which will take effect on the start of the next tone

cycle. The tone signal is guaranteed to have a smooth transition to the new frequency Figure 20-4 shows an

example of increasing frequency with smooth transition on the tone signal.

G litch free

To n e :

25 5

C o unter

O u tput:

w r itin g a n ew va lu e to T oneG en r egister

Figure 20-4. Tone Generator Frequency Change

20.3.1 Tone/AltTone

The signal generator called Tone, has the ability to generate a dual-tone output. The output frequency switch time

and total cycle time are both programmable from 0 to 104.8mS with a step resolution of 102.4uS. Figure 1-5 is a

block diagram of the Tone signal generator. Frequency Register 1 and 2 hold the value of the two alternating

frequencies. Switch time specifies the time at which the output frequency stitches from Freq1 to Freq2. The total

time register sets the total time of the repeating pattern. Figure 1-6 shows the timing diagram of when the output

frequency counter switches between Freq1 and Freq2. Figure 1-7 depicts a waveform of a dual-tone output

pattern showing what settings effect what portion of the output. Figure 1-8 is a block diagram of the AltTone

frequency generator.

Frequency Register1

10 Bits

Frequency Register 2

10 Bits

Tot Time Cnter 0 - 104.8mS

10 Bits

Sw Time Cnter 0 - 104.8mS

10 Bits

Select

Freq Out

Reset

PSF

Div 8

PST

Div 16

ICLK/8

6.4uS

102.4uS

Total Time Register

Switch Time Register

Div 2

Carry

Out

IPB_DI

Figure 20-5. Dual-Tone Tone Generator Block Diagram

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