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CHAPTER 4 INTERFACES
72
Figure 4-11. Little Endian Format
Halfword 1
Halfword 0
Byte 3
Byte 2
Byte 1
Byte 0
AD31
AD16 AD15
AD0
In big endian format, the MSB is stored to the lowest address byte. Bits 31 through 24 of a data word are
stored to byte 0, while bits 7 through 0 are stored to byte 3.
Figure 4-12. Big Endian Format
Halfword 0
Halfword 1
Byte 0
Byte 1
Byte 2
Byte 3
AD31
AD16 AD15
AD0
Only transmit/receive data is subjected to byte order switching based on the little/big endian setting. Other
information is always output to the bus, in the format described in this manual. For such information, the user
need not check the byte order based on whether little or big endian is selected.
Receive indication
Transmit indication
Packet descriptor
Buffer descriptor
Receive batch link pointer
Buffer address and size within receive batch
Data output in fixed format
Indication of words 12 through 15 of raw cell data
Receive cell data
Transmit cell data
Data output in byte order depending
on little/big endian setting
Data of words 0 through 11 of raw cell data
Caution The raw cell data transferred to system memory by the
μ
PD98405 consists of data and
indication sections. The data section, which consists 12 words from word 0 to word 11, is
stored in byte order depending on the little/big endian setting. The indication section, which
consists of four words from word 12 to word 15 is, however, stored in the format described in
this manual, regardless of the little/big endian setting. Note, therefore, that the data and
indication sections are handled differently.