CS8920 datasheet(46/66 Pages) CIRRUS

46 / 66 page

AN84REV1

CS8920 Technical Reference Manual

3.3.10 16-bit Checksum

The checksum stored at the end of the

block is the 2’s complement of the 16-bit

sum of all the preceding words in the

Driver Configuration Block. (The drivers

access the Configuration Block as 16-bit

words.) Any carry out of the 16th bit is

ignored. Since this checksum value is

calculated as the 2’s complement of the

sum of all the preceding words in the block,

a total of 0 should result when the

checksum value is added to the sum of the

previous words. (Must be initialized by

OEM before shipping adapter.)

3.3.11 EISA ID

The two EISA words make up the 32-bit

EISA Product Identification Code.

Low Word

These 16 bits make up the 3-letter identifier

string of the OEM’s EISA ID in 5-bit

compressed ASCII. (A = 00001, B =

00010, C = 00011, etc.)

Bits 7-0: High order 8 bits of 16-bit value

Bits 15-8: Low order 8 bits of 16-bit value

High Word

These 16 bits make up the OEM’s product

ID No.

The upper order 11 bits are the product ID

number and the lower order 5 bits are the

revision number.

Bits 7-0: High order 8 bits of 16-bit value

Bits 15-8: Low order 8 bits of 16-bit value

3.3.12 Serial Number

The two serial number words make up the

unique 32-bit OEM serial number for the

adapter.

Low Word

Bits 7-0: bits[7-0] of 32-bit serial number

Bits 15-8: bits[15-8] of 32-bit serial

number

High Word

Bits 7-0: bits[31-24] of 32-bit serial

number

Bits 15-8: bits[23-16] of 32-bit serial

number

3.3.13 LFSR Checksum

Word 34h contains an 8-bit LFSR

checksum calculated on the EISA ID and

OEM serial number (words 30h to 33h).

The 8-bit LFSR checksum is placed in the

low byte of 34h. The high byte is padded

with the constant 0Ah.

3.4 Recommended Plug and Play

Resource Data

Card resource data stored in the EEPROM

starting at word Address 30h is required for

the CS8920 to implement Plug and Play

operation in accordance with the

Microsoft/Intel Plug and Play Specification.

This information is used by the PnP BIOS

and/or PnP operating system to isolate the

CS8920 adapter and attempt to assign

conflict-free ISA resources.

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