ISD3900
Publication Release Date: Dec 10, 2013
- 72 -
Revision 1.5
FIFO
SPI OUT
SPI IN
UP
SAMPLE
FILTER
DOWN
SAMPLE
FILTER
DECOMPRESSOR
COMPRESSOR
MEMORY
CONTROL
Figure 13-6 SPI Received Encoded Data
RDY/BSYB pin will handshake dataflow to the sample rate and compression bit rate set by the audio
configuration register. If host cannot keep up with data rate compressed audio will be corrupt.
The RDY/BSYB pin will go low whenever the internal FIFO is empty. If no path is set up then
RDY/BSYB pin will be low until command is terminated. If RDY/BSYB is ignored then an OVF_ERR
interrupt is generated. The SPI_RCV_ENC 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_RCV_ENC operations, however care must be taken to
maintain the required data rate to avoid audio corruption.
13.2
D
EVICE
S
TATUS
C
OMMANDS
.
This section describes the 5 status commands that can be sent to the device.
13.2.1 Read Status
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READ_STATUS
Byte Sequence:
Host controller
0x40
0xXX
ISD3900
Status Byte
Interrupt Status Byte
Description:
Query device status.
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READ_STATUS
Byte Sequence:
Host controller
0x40
0xXX
ISD3900
Status Byte 80h
00h
Description:
Query device status.