MT91L62AS datasheet(4/17 Pages) MITEL

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MT91L62

Advance Information

7-176

Table 2: Bit Clock Rate Selection

TxMute pin is high. When either of these pins are low

their respective paths function normally. The -Zero

entry of Table 1 is used for the quiet code deﬁnition.

SSI Mode

The SSI BUS consists of input and output serial data

streams named Din and Dout respectively, a Clock

input signal (CLOCKin), and a framing strobe input

(STB). A 4.096 MHz master clock is also required for

SSI operation if the bit clock is less than 512 kHz.

The timing requirements for SSI are shown in

Figures 5 & 6.

In SSI mode the MT91L62 supports only B-Channel

operation. Hence, in SSI mode transmit and receive

B-Channel data are always in the channel deﬁned by

the STB input.

The data strobe input STB determines the 8-bit

timeslot used by the device for both transmit and

receive data. This is an active high signal with an 8

kHz repetition rate.

SSI operation is separated into two categories based

upon the data rate of the available bit clock. If the bit

clock is 512 kHz or greater then it is used directly by

the

internal

MT91L62

functions

allowing

synchronous operation. If the available bit clock is

128 kHz or 256 kHz, then a 4096 kHz master clock is

required to derive clocks for the internal MT91L62

functions.

Applications where Bit Clock (BCL) is below 512 kHz

are designated as asynchronous. The MT91L62 will

re-align its internal clocks to allow operation when

the external master and bit clocks are asynchronous.

Control pins CSL2, CSL1 and CSL0 are used to

program the bit rates.

For synchronous operation, data is sampled from

Din, on the falling edge of BCL during the time slot

deﬁned by the STB input. Data is made available, on

CSL2

CSL1

CSL0

External

Clock Bit

Rate

(kHz)

CLOCKin

(kHz)

128

4096

256

4096

512

1536

2048

4096

Figure 3 - Audio Gain Partitioning

Serial

Port

Filter/Codec and Analog Interface

PCM

Receive

Filter Gain

0 dB

Receiver

Driver

0 dB

Aout +

Aout-

20k

Ω

Internal To Device

External To Device

Default Bypass

AIN+

AIN-

Transmit Gain

6 dB

PCM

Analog

Input

Din

Dout

Decoder

Encoder

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