CS42516 datasheet(75/90 Pages) CIRRUS

75 / 90 page

DS583F1

CS42516

9.2.1

Channel Status Data E Buffer Access

The user can monitor the incoming Channel Status data by reading the E buffer, which is mapped into the

ured to point to the address space of the C data. This is accomplished by setting the BSEL bit to ‘0’ in the

The user can configure the Interrupt Mask Register to cause an interrupt whenever any data-bit changes

are detected when D to E Channel Status buffer transfers occur. If no data bits have changed within the

current transfer of data from D to E, no interrupt will be generated. This allows determination of the ac-

ceptable time periods to interact with the E buffer. See “Interrupt Mask (address 21h)” on page 64 for more

details.

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 26). There are two methods of accessing this memory, known

as One-Byte Mode and Two-Byte Mode. The desired mode is selected by setting the CAM bit in the Chan-

nel Status Data Buffer Control Register.

9.2.1.1

One-Byte Mode

In many applications, the channel status blocks for the A and B channels will be identical. In this situation,

the user may read a byte from one of the channel's blocks since the corresponding byte for the other chan-

nel will likely be the same. 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.

One-Byte Mode saves the user substantial control port access time, as it effectively accesses two bytes

worth of information 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, can be done especially effi-

ciently.

9.2.1.2

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 interested 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 CS42516 to output two bytes from its control port. The first byte out will

represent the A channel status data, and the second byte will represent the B channel status data.

Control Port

From

S/PDIF

Receiver

words

8-bits

Received

Data

Buffer

Figure 26. Channel Status Data Buffer Structure

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