MT8880 Просмотр технического описания (PDF) - Mitel Networks

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MT8880

ISO²-CMOS Integrated DTMF Transceiver

Mitel Networks 

MT8880C/MT8880C-1 ISO2-CMOS

BIT NAME

FUNCTION

DESCRIPTION

b0 BURST

BURST MODE

A logic ‘0’ enables the burst mode. When this mode is

selected, data corresponding to the desired DTMF tone pair

can be written to the Transmit Register resulting in a tone

burst of a specific duration (see AC Characteristics).

Subsequently, a pause of the same duration is induced.

Immediately following the pause, the Status Register is

updated indicating that the Transmit Register is ready for

further instructions and an interrupt will be generated if the

interrupt mode has been enabled. Additionally, if call

progress (CP) mode has been enabled, the burst and pause

duration is increased by a factor of two. When the burst

mode is not selected (logic ‘1’) tone bursts of any desired

duration may be generated.

b1

TEST

TEST MODE

By enabling the test mode (logic’1’), the IRQ/CP pin will

present the delayed steering (inverted) signal from the DTMF

receiver. Refer to Figure 9 (b3 waveform) for details

concerning the output waveform. DTMF mode must be

selected (CRA b1=0) before test mode can be implemented.

b2

S/D

SINGLE /DUAL TONE

GENERATION

A logic ‘0’ will allow Dual Tone Multi-Frequency signals to be

produced. If single tone generation is enabled (logic ‘1’),

either row or column tones (low group or high group) can be

generated depending on the state of b3 in Control Register

B.

b3

C/R

COLUMN/ROW TONES When used in conjunction with b2 (above) the transmitter

can be made to generate single row or single column

frequencies. A logic ‘0’ will select row frequencies and a logic

‘1’ will select column frequencies.

Table 6. Control Register B Description

BIT

NAME

b0

IRQ

b1 TRANSMIT DATA

REGISTER EMPTY

(BURST MODE ONLY)

b2 RECEIVE DATA

REGISTER FULL

b3 DELAYED STEERING

STATUS FLAG SET

STATUS FLAG CLEARED

Interrupt has occurred. Bit one (b1) Interrupt is inactive. Cleared after

or bit two (b2) is set.

Status Register is read.

Pause duration has terminated

and transmitter is ready for new

data.

Valid data is in the Receive Data

Register.

Cleared after Status Register is

read or when in non-burst mode.

Cleared after Status Register is

read.

Set upon the valid detection of the Cleared upon the detection of a

absence of a DTMF signal.

valid DTMF signal.

Table 7. Status Register Description

4-42

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