AS2578BP datasheet(6/22 Pages) AMSCO

6 / 22 page

Data Sheet

Rev. 3

AS2578 /B

March 1997

data transmission and await the stop condition to return

to the standby power mode.

data

change

data

stable

SDA

SCL

Figure 1 Data Validity

start

bit

stop

bit

SDA

SCL

Figure 2 Definition of Start and Stop

SCL from

master

Data out

from Tx

Data out

from Rx

start

acknowledge

Figure 3 Acknowledge Response From Receiver

FrequencyComparator

The frequency comparator monitors that the ring signal

is in the limits as shown in figure 4.

Tone Generator

The tone generator incorporates the DTMF tones and 3

basic frequencies for the tone ringer.

DTMF

The DTMF generator provides 8 frequencies, namely:

Low group

Row 1

697 Hz

Row 2

770 Hz

Row 3

852 Hz

Row 4

941 Hz

High group

Col. 1

1209 Hz

Col. 2

1336 Hz

Col. 3

1477 Hz

Col. 6

1633 Hz

(AS2578B only)

The MF tones are in accordance with CEPT

recommendations.

Tone Ringer (Melody)

The three basic frequencies of the melodies are:

F1 = 800 Hz, F2 = 1067 Hz, and F3 = 1333 Hz (

± 5%).

The repetition rate can be set via key procedures or by

pin options as follows:

LM code

Repetition rate

1 time

(50 ms pause)

2 (default)

4 times

7 times

10 times

Repetition rate means that a sequence of 6 frequencies

is repeated 1 to 10 times within 1 sec. For LM code 1 a

pause of 50 ms is inserted between the frequencies to

allow a better recognition of the melodies.

The sequence of the frequencies is controlled by the

sequence register as follows:

Sequence

F1 F2 F3 F1 F2 F3 …

The volume of the melodies (MO output) can be set as

follows:

LM code

Volume

Steps

- 17.5 dB

- 11.5 dB

6 dB

- 5.5 dB

6 dB

(default)

0 dB

5.5 dB

When a continious valid ring signal is present for 80 ms,

the melody generator is activated and remains active

until two or more periods of the ring signal are missing.

Ring

frequency

(Hz)

MUST

DETECT

Tol.

Figure 4 Detection Window of Ringing Signal

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