PM3350-SW datasheet(62/224 Pages) PMC

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ELAN 8X10

PM3350 ELAN 8 X10

DATA SHEET

PMC-970109

ISSUE 3

8 PORT ETHERNET SWITCH

PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND PMC-SIERRA, INC. CUSTOMERS ONLY

internal instruction RAM of the Switch Processor rather than a block of

external memory. This bit should be set only if the EightBit flag is also set

(i.e., for a standard 8-bit-wide boot image).

JmpInt:

The JmpInt bit signifies, if set, that the BOOTSTART address indicates an

address present in the instruction RAM of the Switch Processor, rather than

an address in a block of external memory. This bit should be set only if the

EightBit flag is also set (i.e., for a standard 8-bit-wide boot image).

In general, the HDRFLAGS field should be set to 0x80 hex, i.e., indicating an 8-bit-wide

boot image with no special copy or branch options.

Note that the boot image header above is described as it would appear in the 8-bit

image contained within an EPROM or EEPROM that is connected to the least-

significant byte lane of the memory data bus. Each byte within the EPROM or

EEPROM, therefore, will start on a 32-bit boundary and occupy the least-significant 8

bits of a memory word; the upper 24 bits of the word will be ignored by the ELAN 8x10.

The ELAN 8x10 will copy data bytes from the EPROM or EEPROM boot image to

consecutive byte addresses in a block of 32-bit wide RAM, thereby converting the 8-bit

boot image to a 32-bit boot image. An alternative view of the boot header, giving the

components of the header as they would appear after the boot image has been copied

to 32-bit RAM, is given below:

0x59

0x37

0xa8

0xc8

CPYTARGET[23:0]

HDRFLAGS[7:0]

CPYFROM[15:0]

CPYSIZE[15:0]

BOOTSTART[23:0]

CPYFROM[23:16]

CHECKSUM[31:0]

SPACER[31:0]

The CPYTARGET, CPYSIZE and CPYFROM fields of the header define a block

transfer that must be performed from the boot image to an area of RAM in order to

convert the 8-bit boot image to a 32-bit image. After the copy and conversion has been

done, the BOOTSTART field denotes a 24-bit address from which the ELAN 8x10

Switch Processor will begin executing code. The code at this location (presumably

within the copied 32-bit boot image) is completely responsible for initializing the ELAN

8x10 system and environment, and for initiating normal operation.

The CHECKSUM field contains a 32-bit checksum computed over the entire boot

image. The bootstrap firmware will recompute this checksum and compare it with the

value in the CHECKSUM field. If a mismatch occurs, the ELAN 8x10 will consider the

boot image as invalid, and will terminate the system initialization and startup process

and report an error.

PM3350-SW Datasheet(PDF) 62 Page - PMC-Sierra, Inc

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