MT91L60AS datasheet(5/20 Pages) MITEL

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Advance Information

MT91L60

7-111

Companding law selection for the Filter/Codec is

provided by the A/µ companding control bit while

the coding scheme is controlled by the Smag/ITU-T

control bit. The A/

µ control bit is logically OR’ed with

the A/

µ pin providing access in both controller and

controllerless modes.

Both A/

µ and Smag/ITU-T

reside in Control Register 2 (address 04h). Table 1

illustrates these choices.

Table 1

Transducer Interfaces

Standard handset transducer interfaces are provided

by the MT91L60. These are:

• The handset microphone inputs (transmitter),

pins M+/M-. The nominal transmit amplifier gain

may be adjusted to either 6.0 dB or 15.3 dB.

Code

Sign/

Magnitude

ITU-T (G.711)

µ-Law

A-Law

+ Full Scale

1111 1111

1000 0000

1010 1010

+ Zero

1000 0000

1111 1111

1101 0101

-Zero

(quiet code)

0000 0000

0111 1111

0101 0101

- Full Scale

0111 1111

0000 0000

0010 1010

Control of this gain is provided by the TxINC

control bit (Gain Control register 1, address 00h).

• The handset speaker outputs (receiver), pins

HSPKR+/HSPKR-. This internally compensated

fully differential output driver is capable of driving

the load shown in Figure 4. The nominal handset

receive path gain may be adjusted to either 0 dB,

-6 dB or -12 dB. Control of this gain is provided

by the RxINC control bit (Gain Control register 1,

address 00h). This gain adjustment is in addition

to the programmable gain provided by the receive

filter.

Figure 4 - Handset Speaker Driver

HSPKR +

HSPKR -

Ω

150 ohm

load

(speaker)

MT91L60

Figure 3 - Audio Gain Partitioning

Serial Port

Filter/Codec and Transducer Interface

Handset

Receiver

(150

Ω)

PCM

Receive

Filter Gain

0 to -7 dB

(1 dB steps)

Side-tone

-9.96 to

+9. 96 dB

-11 dB

(3.32 dB steps)

-6 dB

Receiver

Driver

-6.0 dB or

0 dB

HSPKR +

HSPKR -

Ω

INTERNAL TO DEVICE

EXTERNAL TO DEVICE

Default Bypass

M+

M-

Transmit

Gain

6.37 dB

Transmit Gain

-0.37 dB or 8.93 dB

Transmit Filter

Gain

0 to +7 dB

(1 dB steps)

PCM

Transmitter

Microphone

Din

Dout

Transmit Filter

Gain

0 to +7 dB

(1 dB steps)

Ω

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