AMBE-2000™ Vocoder Chip

User’s Manual Version 3.0

page 21

Confidential Proprietary, Subject to Change

4.3

Channel Serial Mode

The signals in Table 4-C make up the serial channel interface. The serial channel mode transfers data in and out of the AMBE-

2000™ using 16 bit words on the two data lines CHAN_RX_DATA and CHAN_TX_DATA. The selection of the

formatted or unformatted format of this data is made using information in Table 4-A.

Table 4-C Channel Serial Interface Pin Descriptions

Pin

Symbol

Pin

Direction

Pin

Number

Description

EPR

Out

20

Encoder Packet Ready: Following a reset, this output signal will have a

high to low transition to indicate that the encoder has a frame of data to

output. The next packet will be ready approximately 20 msec later. See

Note 1.

CHAN_RX_DATA

In

32

Serial Data Input: 16 bits of channel data are input on CHAN_RX_DATA,

synchronous to CHAN_RX_CLK, with each CHAN_RX_STRB pulse.

CHAN_RX_CLK

In

28

Serial

Input

Clock:

In

coordination

with

CHAN_RX_STRB,

CHAN_RX_DATA is latched by the AMBE-2000™ on the falling edges of

CHAN_RX_CLK.

CHAN_RX_STRB

In

30

Input (Write) Data Strobe: This signal indicates to the AMBE-2000™

when the data on CHAN_RX_DATA will be latched by CHAN_RX_CLK.

See Figure 4-B.

CHAN_TX_DATA

Out

42

Serial

Data

Output:

16

bits

of

channel

data

are

output

on

CHAN_TX_DATA,

synchronous

to

CHAN_TX_CLK,

with

each

CHAN_TX_STRB pulse.

CHAN_TX_CLK

In

34

Serial Output Clock: In coordination with CHAN_TX_STRB, the data on

CHAN_TX_DATA is output by the AMBE-2000™ on the falling edges of

CHAN_TX_CLK.

CHAN_TX_STRB

Active

Output/

Passive

Input

38

Output (Read) Data Strobe: This signal indicates to the AMBE-2000™

when to bring the data to the CHAN_TX_DATA pin. See Figure 4-B.

Note 1:The AMBE-2000 expects an encoder packet to be read approximately every 20 msec. Following the initial

reset, wait for EPR to go low and read the initial packet (t0). 20 msec later, the next packet (t1) should be ready.

For packet t1 and all following packets use the procedure below:

1) Wait for slightly less than 20 msec.

2) Assert CHAN_TX_STB and read word on CHAN_TX_DATA.

3) If transmitted word not 0x13EC, discard it and repeat step 2.

4) If transmitted word 0x13EC, read 23 more words (rest of packet).

A new packet should be ready every 20 msec after the initial EPR high to low transition.

A packet read should take place

every 20 msec. If there is a delay in the read (i.e. a packet is missed), it is recommended that the device be reset.