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CS8900-CQ

Highly-Integrated ISA Ethernet Controller

Cirrus Logic 

CS8900

either type of EEPROM. The CS8900 will auto-

matically generate sequential addresses while

reading the Reset Configuration Block if a non-

sequential EEPROM is used.

Checking EEPROM for presence of Reset Con-

figuration Block: The read-out of either a binary

101X-XXX0 or 101X-XXX1 (X = do not care)

from the high byte of the header indicates the

presence of configuration data. Any other read-

out value terminates initialization from the

EEPROM. If an EEPROM is attached but not

used for configuration, Crystal recommends that

the high byte of the first word be programmed

with 00h in order to ensure that the CS8900 will

Word Address

00h

01h

02h

03h

04h

05h

06h

07h

08h

09h

0Ah

0Bh

0Ch

0Dh

0Eh

0Fh

10h

Value

A120h

2020h

0300h

0003h

0001h

502Ch

E000h

000Fh

0000h

000Dh

C000h

000Fh

2158h

0010h

0000h

0000h

2800h

Description

FIRST WORD in DATA BLOCK

Configuration Block Header.

The high byte, A1h, indicates a ’C46 EEPROM is attached. The Link Byte, 20h, indicates

the number of bytes to be used in this block of configuration data.

FIRST GROUP of WORDS

Group Header for first group of words.

Three words to be loaded, beginning at 0020h in PacketPage memory.

I/O Base Address

Interrupt Number

DMA Channel Number

SECOND GROUP of WORDS

Group Header for second group of words.

Six words to be loaded, beginning at 002Ch in PacketPage memory.

Memory Base Address - low word

Memory Base Address - high word

Boot PROM Base Address - low word

Boot PROM Base Address - high word

Boot PROM Address Mask - low word

Boot PROM Address Mask high word

THIRD GROUP of WORDS

Group Header for third group of words.

Three words to be loaded, beginning at 0158h in PacketPage memory.

Individual Address - IA bits [39-32], bits [47-40]

Individual Address - IA bits [23-16], bits [31-24]

Individual Address - IA bits [7-0], bits [15-8]

CHECKSUM Value

The high byte, 28h, is the Checksum Value. In this example, the checksum

includes word addresses 00h through 0Fh. The hexadecimal sum of the bytes

is D7h, resulting in a 2’s complement of 28h. The low byte, 00h, provides a

pad to the word boundary.

*FFFFh is a special code indicating that there are no more words in the EEPROM.

Table 3.6. EEPROM Configuration Block Example

18

DS150PP2

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