Cirrus Logic CS8406 - Manual (Page 37)

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CS8406
troller. This is also true if the channel status data is entered serially through the COPY/C pin when the part
is in Hardware Mode.
16.1.2 Serial Copy Management System (SCMS)
In Software Mode, the CS8406 allows read/modify/write access to all the channel status bits. For Con-
sumer Mode SCMS compliance, the host microcontroller needs to manipulate the Category Code, Copy
bit and L bit appropriately.
In Hardware Mode, the SCMS protocol can be followed by either using the COPY and ORIG input pins,
or by using the C bit serial input pin. These options are documented in the Hardware Mode section of this
data sheet.
16.1.3 Channel Status Data E Buffer Access
The E buffer is organized as 24 x 16-bit words. For each word the MS Byte is the A channel data, and the
LS Byte is the B channel data (see Figure 17 ).
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.
16.1.3.1 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. Similarly, 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 chan-
nel 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 CS8406 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 information in 1 byte's worth of access time. If th e 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.
E to F interrupt occurs
Optionally set E to F inhibit
If set, clear E to F inhibit
Return
Write E data
Wait for E to F transfer
Figure 18. Flowchart for Writing the E Buffer