3. Processor Bus Interface
104
PowerSpan II User Manual
80A1010_MA001_09
Integrated Device Technology
www.idt.com
3.4.2.2
Transaction Length
The PB Master can generate a super-set of the data transfer sizes supported by the embedded PowerPC
family. The user can disable certain data transfer sizes that are unique to the PowerQUICC II. All data
transfer sizes supported by the PowerSpan II PB master are illustrated in
below. Burst
transfers are indicated by the assertion of Processor Bus Transfer Burst (PB_TBST_, see
). PB_TBST_ is negated during single cycle transactions (see
below).
The shaded regions in
indicate transaction sizes that are unique to the PowerQUICC II. The
extended cycles supported by the PowerQUICC II are identified with an additional size pin, Processor
Bus Transfer Size (PB_TSIZ[0]). Extended cycles are enabled using the EXTCYC bit in the
Bus Miscellaneous Control and Status Register” on page 304
The following figures,
, illustrate burst reads and burst writes on the PB
Master.
PowerSpan II only interfaces to 64-bit slaves.
Table 22: 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