Specifications

AMBE-3000™ Vocoder Chip Users Manual
Version 2.8, August, 2011
I/
O Management
lo
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
t
a
t
a
<= 5µs (600ns typical)
t
b
System Dependent
t
c
< 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
a
+ t
b
+ t
c
all determines what the maximum rate is. The lower t
b
is the faster the transfer rate. The transfer rate is as
follows:
Transfer Rate (bits/sec) = 8 / (t
a
+ t
b
+ t
c
)
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
b
< 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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