CS8920 datasheet(40/66 Pages) CIRRUS

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AN84REV1

CS8920 Technical Reference Manual

Typically, transmission is enabled by the

MAC driver during its initialization stage.

3.2.2.4 BootPROM Considerations

In all cases, if a BootPROM is installed to

the CS8920 adapter, the adapter should be

activated from the Reset Configuration

Block. In legacy systems, the BootPROMs

base address and address mask must also

be loaded into PacketPage registers from

the Reset Configuration Block as shown in

Table 3.4.

Addr

Word

Description

...

07h

2340

3 words into PacketPage 340h

08h

800Ch

Base Address = 0C8000h

09h

FF00h

Use address lines [23:16], 8-bit device

0Ah

00C0h

Use address lines [15:14]

0Bh

0330h

1 word to PacketPage 330h (RegActivate)

0Ch

0001h

Activate Adapter

0Dh

XX00h

Checksum on 28 bytes

Table 3.4. Configuration of BootPROM

from Reset Configuration Block.

If the adapter is installed in a PnP system

with an autoconfiguring BIOS, the

BootPROM address and mask will be

assigned during the PnP configuration

sequence and should not be loaded from the

Reset Configuration Block.

3.2.2.5 Performance Considerations of

Reset Configuration Block

Software resets may occur frequently and

performance will be enhanced if chip re-

initialization takes as little time as possible.

Therefore, since EEPROM readout takes

approximately 25

µsec. per word, the

length of the Reset Configuration Block

should be kept to a minimum.

3.3 Format of the Driver

Configuration Block

The region of EEPROM addressed as word

addresses 1Ch to 34h is referred to as the

Driver Configuration Block. It is used by

the MAC driver to determine adapter

configuration information such as the

unique IEEE physical address , hardware

version, media capabilities, and bus

configuration (IRQ, DMA, and memory).

This region is called the Driver

Configuration Block.

Table 3.2 defines the format for the Driver

Configuration Block required for use with

MAC drivers provided by Crystal. Crystal

recommends all fields be initialized to their

default values before shipping the adapter.

Default values for each field are indicated

in sections 3.3.1 through 3.3.13. All

reserved fields should be set to zero.

Note: words 30h - 34h are also used as by

PnP as the Serial Identifier block for the

adapter.

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