MT9094AP 查看數據表（PDF） - Zarlink Semiconductor Inc

零件编号

产品描述 (功能)

比赛名单

MT9094AP

ISO2-CMOS ST-BUS™ FAMILY Digital Telephone (DPhone-II)

Zarlink Semiconductor Inc 

MT9094

Data Sheet

0

0 1 Transmit and receive gain control program; with autonulling of the transmit PCM, if the AUTO bit is

set (see address 1Dh)

0

1 0 DTMF generation plus transmit and receive gain control program (autonull available via the AUTO

control bit)

0

1 1 Tone ringer plus transmit and receive gain control program (autonull available via the AUTO control

bit)

1

0 0 handsfree switching program

1

01

1

1 0 Last three selections reserved

1

11

Note: For the DSP to function it must be selected to operate, in conjunction with the Filter/Codec, in one of the B-Channels.

Therefore, one of the B-Channel enable bits must be set (see Timing Control, address 15h: bits CH2EN and CH3EN).

Power Up Reset Program

A hardware power-up reset (pin 6, PWRST) will initialize the DSP hardware registers to the default values (all

zeros) and will reset the DSP program counter. The DSP will then be disabled and the PCM streams will pass

transparently through the DSP. The RAM-based registers are not reset by the PWRST pin but may be initialized to

their default settings by programming the DSP to execute the power up reset program. None of the micro-programs

actually require the execution of the power up reset program but it is useful for pre-setting the variables to a known

condition. Note that the reset program requires one full frame (125µSec) for execution.

Gain Control Program

Gain control is performed on converted linear code for both the receive and the transmit PCM. Receive gain control

is set via the hardware register at address 1Dh (see bits B0 - B5) and may be changed at any time. Gain in 1.5 dB

increments is available within a range of +22.5 dB to -72 dB. Normal operation usually requires no more than a +20

to -20 dB range of control. However, the handsfree switching algorithm requires a large attenuation depth to

maintain stability in worst case environments, hence the large (-72 dB) negative limit. Transmit gain control is

divided into two RAM registers, one for setting the network level of transmit speech (address 20h) and the other for

setting the transmit level of DTMF tones into the network (address 21h). Both registers provide gain control in

1.5 dB increments and are encoded in the same manner as the receive gain control register (see address 1Dh, bits

B0 - B5). The power up reset program sets the default values such that the receive gain is set to -72.0 dB, the

transmit audio gain is set to 0.0dB and the transmit DTMF gain is set to -3.0 dB (equivalent to a DTMF output level

of -4 dBm0 into the network).

Optional Offset Nulling

Transmit PCM may contain residual offset in the form of a DC component. An offset of up to ±fifteen linear bits is

acceptable with no degradation of the parameters defined in CCITT G.714. The DPhone-II filter/CODEC

guarantees no more than ±ten linear bits of offset in the transmit PCM when the autonull routine is not enabled. By

enabling autonulling (see AUTO in the Receive Gain Control Register, address 1Dh) offsets are reduced to within

±one bit of zero. Autonulling circuitry was essential in the first generations of Filter/Codecs to remove the large DC

offsets found in the linear technology. Newer technology has made nulling circuitry optional as offered in the

DPhone-II.

7

Zarlink Semiconductor Inc.

Share Link: