DM9102DEP datasheet(41/70 Pages) DAVICOM

41 / 70 page

Final

Version: DM9102D-DS-F01

May 10, 2006

7. Functional Description

7.1 System Buffer Management

7.1.1 Overview

The data buffers for reception and the transmission of data

reside in the host memory. They are addressd by the

descriptor list that is also located in another region of the

host memory. All actions for the buffer management are

operated by the DM9102D in conjunction with the software

driver. The data structures and processing algorithms are

described in the following text.

7.1.2 Data Structure and Descriptor List

There are two types of buffers that reside in the host

memory, the transmit buffer and the receive buffer. The

buffers are composed of many distributed regions in the

host memory. They are linked together and controlled by the

descriptor lists that reside in another region of the host

memory. The descriptor list is a chain structure. The content

of each descriptor includes pointer to the buffer, size of the

buffer, command and status for the packet to be transmitted

or received. Each descriptor list starts from the address

setting of CR3 (receive descriptor base address) and CR4

(transmit descriptor base address). Refer to Figure 7-1.

7.1.3 Buffer Management -- Chain Structure Method

As the Chain structure depicted below, each descriptor

contains two pointers, one point to a single buffer and the

other to the next descriptor chained. The first descriptor is

chained to the last descriptor under host driver’s control to

form a looped chain. With this structure, a descriptor can be

allocated anywhere in host memory and is chained to the

next descriptor.

Buffer 1

Descriptor 1

Descriptor N

Packet N

control

buffer address 1

status

own

not valid

next descriptor address

buffer 1 length

Figure 7-1

7.1.4 Descriptor List: Buffer Descriptor Format

(a). Receive Descriptor Format

Each receive descriptor has four double word entries and

may be read or written by the host or the DM9102D. The

descriptor format is shown below with a detailed functional

description.

DM9102DEP датащи(PDF) 41 Page - Davicom Semiconductor, Inc.

DM9102DEP датащи(HTML) 41 Page - Davicom Semiconductor, Inc.

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70

датащи скачать

ссылки URL