CS4265 Datasheet, PDF (51/53 Pages) Cirrus Logic – 105 dB, 24-Bit, 192 kHz Stereo Audio CODEC

CS4265
A flowchart for reading and writing to the E buffer is shown in Figure 45. For writing, the sequence starts after an E
to F transfer, which is based on the output timebase.
Begin
Configure the EFTC status bit as
Rising Edge active.
Read the Status Register
(Reg 0Dh)
Is the EFTC bit set?
No
Yes
Optionally set E to F inhibit
Write E data
If set, clear E to F inhibit
Figure 45. Flowchart for Writing the E Buffer
D.1.2 Serial Copy Management System (SCMS)
The CS4265 allows read/modify/write access to all the channel status bits. For consumer mode SCMS compliance,
the host microcontroller needs to manipulate the Category Code, Copy bit and L bit appropriately.
D.1.3 Channel Status Data E Buffer Access
The E buffer is organized as 24 x 16-bit words. For each word the most significant byte is the A channel data, and
the least significant byte is the B channel data (see Figure 44).
There are two methods of accessing this memory, known as one byte mode and two byte mode. The desired mode
is selected through a control register bit.
D.1.3.1 One Byte mode
In many applications, the channel status blocks for the A and B channels will be identical. In this situation, if the user
reads a byte from one of the channel's blocks, the corresponding byte for the other channel will be the same. Simi-
larly, if the user wrote a byte to one channel's block, it would be necessary to write the same byte to the other block.
One byte mode takes advantage of the often identical nature of A and B channel status data.
When reading data in one byte mode, a single byte is returned, which can be from channel A or B data, depending
on a register control bit. If a write is being done, the CS4265 expects a single byte to be input to its control port. This
byte will be written to both the A and B locations in the addressed word.
One byte mode saves the user substantial control port access time, as it effectively accesses 2 bytes worth of infor-
mation in 1 byte's worth of access time. If the control port's auto increment addressing is used in combination with
this mode, multi-byte accesses such as full-block reads or writes can be done especially efficiently.
D.1.3.2 Two Byte mode
There are those applications in which the A and B channel status blocks will not be the same, and the user is inter-
ested in accessing both blocks. In these situations, two byte mode should be used to access the E buffer.
In this mode, a read will cause the CS4265 to output two bytes from its control port. The first byte out will represent
the A channel status data, and the 2nd byte will represent the B channel status data. Writing is similar, in that two
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