DS580F6

37

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 andB 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.

EtoF 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