Crystal LAN CS8920, Technical Reference Manual, Page: 46 / 67

AN84REV1 46
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.