CS8920 datasheet(37/66 Pages) CIRRUS

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AN84REV1

CS8920 Technical Reference Manual

3.2.1.1 Reset Configuration Block

Header

The word at EEPROM address 0x00 is the

Reset Configuration Block header. The

header indicates the type of EEPROM in

use and the length of the Reset

Configuration Block (the number of bytes

loaded into the CS8920 after reset). It can

also be used to disable the PnP feature of

the CS8920.

The presence of bit patterns 1010b (0xA) or

1011b (0xB) in bits 15-12 of the header

indicate the presence of a Reset

Configuration Block. The plug and play

circuitry of the CS8920 can be disabled by

setting bits 15-12 (high nibble) of the

header to 0xB.

Bit 8 (bit 0 being the LSB of the word) of

the header specifies the type of EEPROM

used. A value of 0 in bit 8 indicates a

sequential EEPROM is used. A value of 1

in bit 8 indicates a non-sequential

EEPROM is used. (The CS8920 works

equally well with either type of EEPROM.

It will automatically generate sequential

addresses while reading the Reset

Configuration Block from non-sequential

type EEPROMs.)

The low byte of the header (bits 7-0)

specify the number of bytes of

configuration data in the Reset

Configuration Block including the first

word and checksum at the end of the block.

Example: a Reset Configuration Block of

0xA10A indicates a valid configuration

block, non-sequential EEPROM, 10 bytes

of configuration data follow, and PnP is

enabled.

3.2.1.2 Configuration Data

Following the Reset Configuration Block

header are one or more groups of

configuration data that are to be

automatically loaded into the CS8920’s

PacketPage registers.

Each group of configuration data consists

of a group header (the first word in the

group) and one or more words of

configuration data. The group header

indicates the number of words in the group

along with the address of the PacketPage

configuration data are to be loaded.

The value in bits 15-12 of the group header

is one less than the total number of

configuration data words in the group. For

example, if bits 15-12 equal 0001, there are

two words of configuration data in the

group.

Bits 9 through 0 of the group header

indicate the 10-bit address of the

PacketPage register the first word of

configuration data in the group is to be

loaded into. If there are additional

configuration data words in the group, they

are loaded in successive PacketPage

registers. See Table 3.1 for an example.

Bits 11 and 10 of the group header are

forced to 0 when read by the CS8920,

restricting the destination address range of

the configuration to the first 1024 bytes of

the PacketPage memory.

3.2.1.3 Checksum

The last word of the Reset Configuration

Block contains an 8-bit checksum in the

CS8920 Datasheet(PDF) 37 Page - Cirrus Logic

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