AMBE-2000™ Vocoder Chip Users Manual
Version 4.92, June, 08
DVSI Confidential Proprietary, Subject to Change
Page 25
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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-2020™ using 16 bit words on the two data lines CHAN_RX_DATA and CHAN_TX_DATA. The selection of the
framed or unframed 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-2020™ on the falling edges of CHAN_RX_CLK.
CHAN_RX_STRB
In
30
Input (Write) Data Strobe : This signal indicates to the AMBE-2020™ 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-2020™ on the rising edges of
CHAN_TX_CLK.
CHAN_TX_STRB
Active Output/
Passive Input
38
Output (Read) Data Strobe : This signal indicates to the AMBE-2020™ when to bring
the data to the CHAN_TX_DATA pin. See figure 4-B.
Note 1:The AMBE-2020™ 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.
