3. Processor Bus Interface
92
PowerSpan II User Manual
80A1010_MA001_09
Integrated Device Technology
www.idt.com
3.3.2
Data Phase
The data phase deals with the control of transaction length.
3.3.2.1
Transaction Length
The PB Slave supports a set of the data transfer sizes supported by the embedded PowerPC family. All
data transfer sizes supported by the PowerSpan II PB Slave are illustrated in
. Burst transfers
are indicated by the assertion of Processor Bus Transfer Burst (PB_TBST_). The shaded regions
indicate transaction sizes unique to the PowerQUICC II.
3.3.2.2
Data Alignment
Embedded processor bus transfer sizes and alignments, defined in
and
, are supported
by the PB Slave for transaction accesses. The shaded table cells in
show transactions that
support the
PowerPC 7400
processor.
lists the size and alignment transactions less than or equal to 8 bytes. PowerSpan II register
accesses are limited to 4 bytes or less.
Table 16: PowerSpan II PB Transfer Sizes
Transfer Size
Bytes
PB_TBST
PB_TSIZ[0]
PB_TSIZ[1:3]
Byte
1
1
0
001
Half-word
2
1
0
010
Tri-byte
3
1
0
011
Word
4
1
0
100
Five bytes
5
1
0
101
Six bytes
6
1
0
110
Seven bytes
7
1
0
111
Double Word (DW)
8
1
0
000
Extended Double (PowerQUICC II
only)
16
1
1
001
Extended Triple (PowerQUICC II only)
24
1
1
010
Burst (Quad DW)
32
0
0
010
The PowerSpan II port size is 64-bit.