DM9302 datasheet(48/64 Pages) DAVICOM

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DM9302

10/100Mbps Ethernet Fiber/Twisted Pair Media Converter with Local bus

Preliminary datasheet

DM9302-15-DS-P01

July 30, 2009

9. FUNCTIONAL DESCRIPTION

9.1 Processor bus and memory management function:

9.1.1 Processor Interface

In the general processor mode, the chip selection

is just coming from pin CS#. There are only two

addressing ports through the access of the host

interface.

One port is the INDEX port and the other is the

DATA port. The INDEX port is decoded by the CMD

pin=0 and the DATA by the CMD pin=1. The contents

of the INDEX port are the register address of the

DATA port. Before the access of any register, the

address of the register must be saved in the INDEX

port before.

9.1.2 Direct Memory Access Control

The DM9302 provides DMA capability to simplify

the access of the internal memory. After the setting of

the starting address of the internal memory and then

issuing a dummy read/write command to load the

current data to internal data buffer, the desired

location of the internal memory can be accessed by

the read/write command registers. The memory’s

address will be increased with the size equal to the

current operation mode (i.e. the byte or word mode)

and the data of the next location will be loaded to

internal data buffer automatically. It is noted that the

data of the first access (the dummy read/write

command) in a sequential burst should be ignored

because that the data was the contents of the last

read/write command.

There are two configured types of internal

memory which are controlled by bit 7 of IMR. When

the bit 7 of IMR is set, the internal memory is used for

transmit and receive buffers. The transmit buffer

occupies 8K bytes. And the receive buffer occupies

7.75K bytes. Both the transmit and receive buffer

address need not to be programmed instead that they

are managed by the DM9302 automatically. In

transmit function, after power on reset or each time

after the transmit command is issued (bit 0 of TCR is

set), the next starting transmit buffer address is

loaded. In receive function, the 7.75K-byte receive

buffer can be treated as a continued logic memory

space. The memory address will wrap to address 0 if

the end of address is reached.

When the bit 7 of IMR is cleared, there is a 64K-

byte memory space in the DM9302 can be accessed.

This configured type of internal memory is used for

testing only. The memory write address (register

FAh/FBh) and the memory read address (register

F4h/F5h) represent the physical memory address of

the DM9302 internal memory. It is noted that after the

memory had been written by memory write command,

the switch reset command (bit 6 of register 52h)

should be set before normal switch function operation,

since the controlled data in internal memory may be

corrupted.

9.1.3 Packet Transmission

There are two packets, sequentially named as

index I and index II, can be stored in the TX SRAM at

the same time. The index register 02h controls the

insertion of CRC.

The start address of transmission is 00h and the

current packet is index I after software or hardware

reset. Firstly write data to the TX SRAM using the

DMA port and then write the byte count to byte count

of control register. The DM9302 starts to transmit the

index I packet. Before the transmission of the index I

packet ends, the data of the next (index II) packet can

be moved to TX SRAM. After the index I packet ends

the transmission, write the byte count data of the

index II to BYTE_COUNT register and then set the bit

1 of control register to transmit the index II packet.

The following packets, named index I, II, I, II… use

the same way to be transmitted.

9.1.4 Packet Reception

The RX SRAM is a ring data structure. Each

packet has a 4-byte header followed with the data of

the reception packet which CRC field is included. The

format of the 4-byte header is 01h, status,

BYTE_COUNT low, and BYTE_COUNT high. It is

noted that the start address of each packet is in the

proper address boundary which depends on the

operation mode (byte or word mode).

DM9302 Datasheet(PDF) 48 Page - Davicom Semiconductor, Inc.

DM9302 Datasheet(HTML) 48 Page - Davicom Semiconductor, Inc.

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