MFC2000 datasheet(361/426 Pages) ETC

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Hardware Description

MFC 2000 Multifunctional Peripheral Controller 2000

100723A

Conexant

20-3

20.2.1 Bell Mode

Firmware operation

The firmware needs to control Bell/Ringer generator to issue the following waveform:

Bell

Qu iet

~ 1 s

~ 2 s

~ 1 s

...

H i-Z

Bell

In order to setup for Bell mode, the following steps must be taken.

Initialize:

Write the desired frequency of bell in BellPeriod register (see Table 20-1)

Allow Hi-Z on output (BellDriveEnb = 0)

Disable ringer mode (RingerEnb = 0)

Start bell signal:

Enable Bell generator (BellEnb = 1)

(This setting will start the counter to run)

Create “Bell-Quiet-Bell” signal:

Once the bell signal has been generated, the firmware will read BellPeriod register. On every Phase A or 9,

the off-hook signal is checked. If it is detected, then the bell signal is disabled by having BellEnb = 0. This will

ensure the bell signal is terminated on the high to high-Z transition.

If after about 1s, the off-hook signal is not detected, then the firmware will disable the bell signal by having

BellEnb = 0 when the phase is on 9. When BellEnb is reset to 0, then the bell signal will stop at the Hi-Z, and

the phase will be in zero. After about 2 s of quiet, the bell signal can be activated again by setting BellEnb

to 1.

20.2.2 Ringer Mode

The Ringer mode of operation requires the use of both the Bell/Ringer generator as well as the ALTTone

generator. The fundamental frequency of this ringer signal is the same as the bell signal. The ringer signal works

in conjunction with the ALTTone Generator to modulated it’s output. The active window for the ring pulses (bell

period high), will automatically shift so that the modulating waveform is not truncated at the beginning or end.

Note: The firmware needs to control Bell/Ringer generator to issue the following waveformn:

Rin g

Qu iet

~ 1 s

~ 2 s

~ 1s

Rin g

...

Figure 20-3. Bell/Ringer Generator Waveform

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