CS8900-IQ 查看數據表（PDF） - Cirrus Logic

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CS8900-IQ

Crystal LAN™ ISA Ethernet Controller

Cirrus Logic 

CS8900A

Crystal LAN™ ISA Ethernet Controller

4.3.5 DMA Start of Frame

(Read only, Address: PacketPage base + 0026h)

Address 0027h

Most significant byte of offset value

Address 0026h

Least significant byte of offset value

The DMA Start of Frame Register contains a 16-bit value which defines the offset from the DMA base address to

the start of the most recently transferred received frame. See Section 5.4 on page 89.

Reset value is: 0000 0000 0000 0000

4.3.6 DMA Frame Count

(Read only, Address: PacketPage base + 0028h)

Address 0029h

Most significant byte of frame count

(most-significant nibble always 0h)

Address 0028h

Least significant byte of frame count

The lower 12 bits of the DMA Frame Count register define the number of valid frames transferred via DMA since the

last readout of this register. The upper 4 bits are reserved. See Section 5.4 on page 89.

Reset value is: XXXX 0000 0000 0000

4.3.7 RxDMA Byte Count

(Read only, Address: PacketPage base + 002Ah)

Address 002Bh

Most significant byte of byte count

Address 002Ah

Least significant byte of byte count

The RxDMA Byte Count register describes the valid number of bytes DMAed since the last readout. See Section 5.4

on page 89.

Reset value is: 0000 0000 0000 0000

4.3.8 Memory Base Address

(Read/Write, Address: PacketPage base + 002Ch)

Address 002Fh

Reserved

Address 002Eh

The most significant nibble of

memory base address. The

high-order nibble is reserved.

Address 002Dh

Contains portion of memory

base address.

Address 002Ch

The least significant byte of

the memory base address.

Memory Base Address: The lower three bytes (002Ch, 002Dh, and 002Eh) are used for the 20-bit memory base

address. The upper three nibbles are reserved.

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 18.

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

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