ISD3900
Publication Release Date: Dec 10, 2013
- 71 -
Revision 1.5
FIFO
SPI OUT
SPI IN
UP
SAMPLE
FILTER
DOWN
SAMPLE
FILTER
DECOMPRESSOR
COMPRESSOR
MEMORY
CONTROL
Figure 13-5 SPI Send Compressed Data to Decode
The RDY/BSYB pin will go low whenever the internal FIFO is full. If no path set up to accept audio
data then RDY/BSYB pin will not return high until command is terminated. If RDY/BSYB is ignored
then an OVF_ERR interrupt is generated. The SPI_SND_DEC command is accepted if no current play
or record operation is active. If command is not accepted a CMD_ERR interrupt will be generated. It is
possible to perform digital memory operations between SPI_SND_DEC operations, however care
must be taken to maintain the required data rate to avoid audio corruption.
13.1.13 SPI Receive Encoded Data
SPI_RCV_ENC
Byte Sequence:
Host controller
0xC2
ISD3900
Status Byte
D0[7:0]
D1[7:0]
….
Dn[7:0]
Description:
Read compressed audio data via SPI interface.
Interrupt
Generation:
OVF_ERR if RDY/BSYB violated.
This command allows the user to receive compressed audio data, in a byte formatted bit stream, from
the SPI interface for use or storage outside the ISD3900. Before execution of command (1) a valid
recording signal path must be set up such that compressor is active. (2) Multiple SPI_RCV_ENC
commands can be sent to receive compressed data from the ISD3900. (3) To finish receiving data a
STOP command is sent and device will generate a CMD_FIN interrupt.