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IDT821068

OCTAL PROGRAMMABLE PCM CODEC

Integrated Device Technology 

IDT821068 OCTAL PROGRAMMABLE PCM CODEC

INDUSTRIAL TEMPERATURE RANGE

output to LMRL and LMRH. When L/C bit is 0, compressed PCM will

be output transparently to LMRH.

The calculation and method of level metering will be described in

Application Note.

TELETAX

The teletax signal is used to sum the telephone fee according to the

calling time and tariff. The frequency of teletax signal carrier can be

selected as 12 kHz or 16 kHz (± 50 Hz) by Global Command 19,

while the amplitude of the teletax signal on specific channel can be

programmed by Teletax Gain Setting bits (TGS[7:0]) in Local Com-

mand 3. When a ‘1’ appears on Teletax Ramp Start bit (RS) of Local

Command 10, the teletax signal will be output from the VOUT pin on

the corresponding channel with a 16 ms ± 10% rising time. This

teletax signal will last until a ‘0’ on the RS bit for the same channel. It

has a falling time of 16 ms ± 10%, as shown in Figure 12.

pause

time

CHANNEL POWER DOWN/STANDBY MODE

Each individual channel of IDT821068 can be powered down

independently by Local Command 10. When the channel is powered

down (enters into standby mode), PCM data transmission and

reception, D/A and A/D are disabled. In this way, power consumption

of the device can be reduced. When IDT821068 is powered up or

reset, all eight channels will be powered down. All circuits that contain

programmed information retain their data when powered down. In MPI

operation, MPI (Microprocessor Interface) is always active so that new

command could be received and executed. In GCI operation, the

monitor channel of any time slot is always on so that new command

could be accepted at any time.

POWER DOWN PLL/SUSPEND MODE

A suspend mode is offered to the whole chip to save power. In this

mode, the PLL block is turned off and DSP operation is disabled. This

mode saves much more power consumption than standby mode. In

this mode, only Global Command and Local Command can be

executed. RAM operation is disabled as internal clock has been

turned off. The PLL blocks can be powered down by Global

Command 25. Suspend mode can be entered by powering down PLL

and all channels.

rising

time

falling time

Figure 12. Teletax Signal

18

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