CS8900A datasheet(22/128 Pages) CIRRUS

22 / 128 page

DS271PP3

CS8900A

Crystal LAN™ ISA Ethernet Controller

CIRRUS LOGIC PRODUCT DATA SHEET

CS8900A will not attempt to read configuration

data from the EEPROM.

3.4.3.5 Determining Number of Bytes in the Reset

Configuration Block

The low byte of the Reset Configuration Block

header is known as the link byte. The value of the

Link Byte represents the number of bytes of config-

uration data in the Reset Configuration Block. The

two bytes used for the header are excluded when

calculating the Link Byte value.

For example, a Reset Configuration Block header

of A104h indicates a non-sequential EEPROM pro-

grammed with a Reset Configuration Block con-

taining 4 bytes of configuration data. This Reset

Configuration Block occupies 6 bytes (3 words) of

EEPROM space (2 bytes for the header and 4 bytes

of configuration data).

3.4.4 Groups of Configuration Data

Configuration data are arranged as groups of

words. Each group contains one or more words of

data that are to be loaded into PacketPage registers.

Word Address

Value

Description

FIRST WORD in DATA BLOCK

00h

A120h

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

01h

2020h

Group Header for first group of words.

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

02h

0300h

I/O Base Address

03h

0003h

Interrupt Number

04h

0001h

DMA Channel Number

SECOND GROUP of WORDS

05h

502Ch

Group Header for second group of words.

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

06h

E000h

Memory Base Address - low word

000Fh

Memory Base Address - high word

08h

0000h

Boot PROM Base Address - low word

09h

000Dh

Boot PROM Base Address - high word

0Ah

C000h

Boot PROM Address Mask - low word

0Bh

000Fh

Boot PROM Address Mask - high word

THIRD GROUP of WORDS

0Ch

2158h

Group Header for third group of words.

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

0Dh

0010h

Individual Address - Octet 0 and 1

0Eh

0000h

Individual Address - Octet 2 and 3

0Fh

0000h

Individual Address - Octet 4 and 5

CHECKSUM Value

10h

2800h

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

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

the bytes is D8h, 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 6. EEPROM Configuration Block Example

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