M-8870-02S Ver la hoja de datos (PDF) - Unspecified

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componentes Descripción

Fabricante

M-8870-02S

DTMF Receiver

Unspecified 

M-8870

Explanation of Events

(A) Tone bursts detected, tone duration invalid, outputs not updated.

(B) Tone #n detected, tone duration valid, tone decoded and latched in outputs.

(C) End of tone #n detected, tone absent duration valid, outputs remain latched until next valid tone.

(D) Outputs switched to high impedance state.

(E) Tone #n + 1 detected, tone duration valid, tone decoded and latched in outputs (currently high impedance).

(F) Acceptable dropout of tone #n + 1, tone absent duration invalid, outputs remain latched.

(G) End of tone #n + 1 detected, tone absent duration valid, outputs remain latched until next valid tone.

Explanation of Symbols

VIN

ESt

St/GT

Q1 - Q4

StD

OE

tREC

tREC

tID

tDO

tDP

tDA

TGTP

TGTA

DTMF composite input signal.

Early steering output. Indicates detection of valid tone frequencies.

Steering input/guard time output. Drives external RC timing circuit.

4-bit decoded tone output.

Delayed steering output. Indicates that valid frequencies have been present/absent for the required guard

time, thus constituting a valid signal.

Output enable (input). A low level shifts Q1 - Q4 to its high impedance state.

Maximum DTMF signal duration not detected as valid.

Minimum DTMF signal duration required for valid recognition.

Minimum time between valid DTMF signals.

Maximum allowable dropout during valid DTMF signal.

Time to detect the presence of valid DTMF signals.

Time to detect the absence of valid DTMF signals.

Guard time, tone present.

Guard time, tone absent.

Figure 8 Timing Diagram

40-406-00011, Rev. F

Page 7

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