CS4265 Datasheet, PDF (50/53 Pages) Cirrus Logic – 105 dB, 24-Bit, 192 kHz Stereo Audio CODEC

CS4265
APPENDIX D: CHANNEL STATUS BUFFER MANAGEMENT
The CS4265 has a comprehensive channel status (C) data buffering scheme which allows the user to manage the
C data through the control port.
D.1 IEC60958-3 Channel Status (C) Bit Management
The CS4265 contains sufficient RAM to store a full block of C data for both A and B channels (192x2 = 384 bits).
The user may read from or write to these RAM buffers through the control port.
The CS4265 manages the flow of channel status data at the block level, meaning that entire blocks of channel status
information are buffered at the input, synchronized to the output time base, and then transmitted. The buffering
scheme involves a cascade of 2 block-sized buffers, named E and F, as shown in Figure 44. The MSB of each byte
represents the first bit in the serial C data stream. For example, the MSB of byte 0 (which is at control port address
13h) is the consumer/professional bit for channel status block A.
The E buffer is accessible from the control port, allowing read and writing of the C data. The F buffer is used as the
source of C data for the IEC60958-3 transmitter. The F buffer accepts block transfers from the E buffer.
A
B
8-bits 8-bits
E
24
words
F
Transm it
D a ta
B u ffe r
To
AES3
Transm itter
Control Port
Figure 44. Channel Status Data Buffer Structure
D.1.1 Accessing the E buffer
The user can monitor the data being transferred by reading the E buffer, which is mapped into the register space of
the CS4265, through the control port. The user can modify the data to be transmitted by writing to the E buffer.
The user can configure the status register such that EFTC bit is set whenever an E to F transfer completes. With
this configuration in place, periodic polling of the status register allows determination of the time periods acceptable
for E buffer interaction.
Also provided is an “E to F” inhibit bit. The “E to F” buffer transfer is disabled whenever the user sets this bit. This
may be used whenever “long” control port interactions are occurring.
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DS657A2