EM78P813

8-bit OTP Micro-controller

__________________________________________________________________________________________________________________________________________________________________

* This specification is subject to change without notice.

23

2004/8/19

(V1.6)

770

1209

4

1

0100

770

1336

5

1

0101

770

1477

6

1

0110

852

1209

7

1

0111

852

1336

8

1

1000

852

1477

9

1

1001

941

1209

0

1

1010

941

1336

*

1

1011

941

1477

#

1

1100

697

1633

A

1

1101

770

1633

B

1

1110

852

1633

C

1

1111

941

1633

D

1

0000

Any

Any

Any

0

xxxx

(x:unknown)

Bit 4~Bit 5 : Unused

Bit 6 (STD) : Delayed steering output.

Presents a logic high when a received tone-pair has been registered and the output latch updated; returns to logic

low when the voltage on St/GT falls below V tst.

0/1

Data invalid/data valid

Be sure open main clock before using DTMF receiver circuit . A logic”0,0” applied to R5 page3 b4 and b3 will

shut down power of the device to minimize the power consumption in a standby mode. It stops functions of the filters.

In many situations not requiring independent selection of receive and pause, the simple steering circuit of is

applicable. Component values are chosen according to the following formulae:

t REC = t DP + t GTP

t ID = t DA + t GTA

The value of t DP is a parameter of the device and t REC is the minimum signal duration to be recognized by the

receiver. A value for C of 0.1 uF is recommended for most applications, leaving R to be selected by the designer. For

example, a suitable value of R for a t REC of 30mS would be 300k.

Different steering arrangements may be used to select independently the guard-times for tone-present (t GTP )

and tone-absent (t GTA ). This may be necessary to meet system specifications which place both accept and reject

limits on both tone duration and inter digital pause.

Guard-time adjustment also allows the designer to tailor system parameters such as talk off and noise immunity.

Increasing t REC improves talk-off performance, since it reduces the probability that tones simulated by speech will

maintain signal condition for long enough to be registered. On the other hand, a relatively short t REC with a long t DO

would be appropriate for extremely noisy environments where fast acquisition time and immunity to drop-outs would be

required.

VDD

ST/GT

EST

VDD

R

C

Fig.16

DTMF receiver delay time control