3. Processor Bus Interface
109
PowerSpan II User Manual
80A1010_MA001_09
Integrated Device Technology
www.idt.com
PowerPC 7400 Transaction Support
The
PowerPC 7400
processors supports misaligned transactions within a double word (64-bit aligned)
boundary. As long as the transaction does not cross the double word boundary, the
PowerPC 7400
can
transfer data on the misaligned address.
PowerSpan II supports a specific types of the
PowerPC 7400
misaligned transactions (shown in
) when the MODE_7400 bit is set in the
“Processor Bus Miscellaneous Control and Status
. Any misaligned transaction between PowerSpan II and the PowerPC 7400 that
is a single word (32-bit) or less must be within a single word aligned boundary. Any transfer greater
than a single word must start or end on a word boundary.
Word
0100
000
D0
D1
D2
D3
0100
001
D1
D2
D3
D4
0100
010
D2
D3
D4
D5
0100
011
D3
D4
D5
D6
0100
100
D4
D5
D6
D7
Five bytes
0101
000
D0
D1
D2
D3
D4
0101
001
D1
D2
D3
D4
D5
0101
010
D2
D3
D4
D5
D6
0101
011
D3
D4
D5
D6
D7
Six bytes
0110
000
D0
D1
D2
D3
D4
D5
0110
001
D1
D2
D3
D4
D5
D6
0110
010
D2
D3
D4
D5
D6
D7
Seven bytes
0111
000
D0
D1
D2
D3
D4
D5
D6
0111
001
D1
D2
D3
D4
D5
D6
D7
Double word
0000
000
D0
D1
D2
D3
D4
D5
D6
D7
is independent of endian considerations and pertains to byte lane
control on the processor bus. For endian considerations, please consult
.
Software must make sure that the
PowerPC 7400
does not initiate unsupported misaligned
transactions to PowerSpan II.
Table 24: PowerSpan II Processor Bus Single Beat Data Transfers
Size
TSIZ[0:3]
A[29:31]
Data Bus Byte Lanes