Digital Voice Systems AMBE-3000 Specifications download pdf (Page 56)

AMBE-3000™ Vocoder Chip Users Manual

Version 2.8, August, 2011

O Management

w. After the AMBE-3000™ Vocoder Chip sets PPT_ACK low, PPT_WRITE pin must set high, at which time, the AMBE-

3000™ Vocoder Chip will set PPT_ACK high.

Figure 25 PPT Interface Timing

PPT Timing

<= 5µs (600ns typical)

System Dependent

< 275 ns

Table 26 PPT Timing

The time between when the AMBE-3000™ Vocoder Chip sets PPT_ACK Low and the user sets PPT_WRITE high has to be

>0. Times t

+ t

all determines what the maximum rate is. The lower t

is the faster the transfer rate. The transfer rate is as

follows:

Transfer Rate (bits/sec) = 8 / (t

+ t

)

At time 1 controller sets PPT_READ (PPT_WRITE) low to request to read (write) from the PPT interface.

At time 2 the AMBE-3000™ Vocoder Chip sets the PPT_ACK low and the PPT_DATA is valid.

At time 3 the controller has read (written) the data and now sets the PPT_READ (PPT_WRITE) high.

At time 4 the AMBE-3000™ Vocoder Chip sets the PPT_ACK high after the PPT_READ (PPT_WRITE) goes back to high.

For Example: If the designed system uses t

< 0.5µs the parallel port can transfer data, at rates exceeding 3.5 Mbps.

5.6 Codec A/D / D/A Interface

The AMBE-3000™ Vocoder Chip operates with a speech data sample rate of 8kHz for both the A/D and D/A interfaces. This

8kHz data is input and output using a serial port on the AMBE-3000™ Vocoder Chip. The user can choose between hardware

configuration pins or software control in order to the process of configuring the interface to the A/D-D/A chip.

5.7 Vocoder Front End Requirements

In order to ensure proper performance from the voice coder, it is necessary for the vocoder front end to meet a set of minimum

performance requirements. For the purposes of this section the vocoder front end is considered to be the total combined

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Digital Voice Systems AMBE-3000 Specifications Page 56