MT3170 datasheet(4/8 Pages) MITEL

4 / 8 page

MT3170B/71B, MT3270B/71B, MT3370B/71B

4-6

Serial Data (SD) Output

When a valid DTMF signal burst is present, ESt or

DStD will go high.

The application of four clock

pulses on the ACK pin will provide a 4-bit serial

binary code representing the decoded DTMF digit on

the SD pin output. The rising edge of the first pulse

applied on the ACK pin latches and shifts the least

significant bit of the decoded digit on the SD pin.

The next three pulses on ACK pin will shift the

remaining latched bits in a serial format (see Figure

5). If less than four pulses are applied to the ACK

pin, new data cannot be latched even though ESt/

DStD can be valid. Clock pulses should be applied

to clock out any remaining data bits to resume

normal operation. Any transitions in excess of four

pulses will be ignored until the next rising edge of the

ESt/DStD. ACK should idle at logic low. The 4-bit

binary representing all 16 standard DTMF digits are

shown in Table 1.

Powerdown Mode (MT317xB/337xB)

The MT317xB/337xB devices offer a powerdown

function to preserve power consumption when the

device is not in use. A logic high can be applied at

the PWDN pin to place the device in powerdown

mode. The ACK pin should be kept at logic low to

avoid undefined ESt/DStD and SD outputs (see

Table 2).

0= LOGIC LOW, 1= LOGIC HIGH

Table 1. Serial Decode Bit Table

Note:

b0=LSB of decoded DTMF digit and shifted out first.

FLOW

FHIGH

DIGIT

697

1209

697

1336

697

1477

770

1209

770

1336

770

1477

852

1209

852

1336

852

1477

941

1336

941

1209

941

1477

697

1633

770

1633

852

1633

941

1633

Table 2. Powerdown Mode

+ =enters powerdown mode on the rising edge.

Table 3. Call Progress Tones

ACK (input)

PWDN (input)

ESt/DStD (output)

SD (output)

MT317xB/337xB

status

low

Refer to Fig. 4 for

timing waveforms

Refer to Fig. 4 for

timing waveforms

normal operation

low

high+

low

powerdown mode

high

low

undefined

high

undefined

Frequency 1 (Hz)

Frequency 2 (Hz)

On/Off

Description

350

440

continuous

North American Dial Tones

425

---

continuous

European Dial Tones

400

---

continuous

Far East Dial Tones

480

620

0.5s/0.5s

North American Line Busy

440

---

0.5s/0.5s

Japanese Line Busy

480

620

0.25s/0.25s

North American Reorder Tones

440

480

2.0s/4.0s

North American Audible Ringing

480

620

0.25s/0.25s

North American Reorder Tones

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