CS8900A datasheet(45/128 Pages) CIRRUS

45 / 128 page

DS271PP3

CS8900A

Crystal LAN™ ISA Ethernet Controller

CIRRUS LOGIC PRODUCT DATA SHEET

4.3.9 Boot PROM Base Address

(Read/Write, Address: PacketPage base + 0030h)

The lower three bytes (0030h, 0031h, and 0032h) of the Boot PROM Base Address register are used for the 20-bit

Boot PROM base address. The upper three nibbles are reserved. See Section 3.6 on page 25.

After reset, if no EEPROM is found by the CS8900A, then the register has the following initial state. If an EEPROM

is found, then the register’s initial value may be set by the EEPROM. See Section 3.3 on page 19.

Reset value is: XXXX XXXX XXXX 0000 0000 0000 0000 0000

4.3.10 Boot PROM Address Mask

(Read/Write, Address: PacketPage base + 0034h)

The Boot PROM address mask register indicates the size of the attached Boot PROM and is limited to 4K bit incre-

ments. The lower 12 bits of the Address Mask are ignored, and should be 000h. The next lowest-order bits describe

the size of the PROM. The upper three nibbles are reserved.

For example:

See Section 3.6 on page 25.

After reset, if no EEPROM is found by the CS8900A, then the register has the following initial state. If an EEPROM

is found, then the register’s initial value may be set by the EEPROM. See Section 3.3 on page 19.

Reset value is: XXXX XXXX XXXX 0000 0000 0000 0000 0000

Address 0033h

Address 0032h

Address 0031h

Address 0030h

Reserved

The most significant nibble of

Boot PROM base address.

The high-order nibble is

reserved.

Contains portion of Boot PROM

base address.

The least significant byte of

the Boot PROM base

address.

Address 0037h

Address 0036h

Address 0035h

Address 0034h

Reserved

The most significant nibble of

Boot PROM mask address.

The high-order nibble is

reserved.

Contains portion of Boot PROM

mask address. The lower-order

nibble must be written as 0h.

The least significant byte of

the Boot PROM mask

address. Must be written as

00h.

Size of Boot PROM

4k bits

XXXX XXXX XXXX 1111 1111 0000 0000 0000

8k bits

XXXX XXXX XXXX 1111 1110 0000 0000 0000

16k bits

XXXX XXXX XXXX 1111 1100 0000 0000 0000

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