2. PCI Interface
40
PowerSpan II User Manual
80A1010_MA001_09
Integrated Device Technology
www.idt.com
Master-based Decode
The PCI Target supports Master-based decode when the PowerSpan II PCI arbiter is enabled (see
). With Master-based decode enabled, a PCI target image only claims a
transaction decoded for its specified physical address space if it originates from a specific PCI master.
External bus masters are selected for a specific target image by setting the corresponding bits in the
“PCI-1 Target Image x Translation Address Register” on page 274
2.2.1.2
Address Translation
The address generated on the destination port is dependent on the use of address translation in the
source target image. For more information, see the Translation Address Enable (TA_EN) bit in the
“PCI-1 Target Image x Control Register” on page 268
. When address translation is enabled
—
by
setting the TA_EN bit
—
the address generated on the destination bus is derived from the following
three inputs:
•
incoming address on the PCI Target
•
block size of the target image
BS[3:0] in the
“PCI-1 Target Image x Control Register” on page 268
•
translation address
TADDR in the
“PCI-1 Target Image x Translation Address Register” on page 274
When address translation is disabled the address on the destination bus is the same as the address on the
source bus.
2.2.1.3
Transaction Type Mapping
A transaction can be mapped to the PB interface or to another PCI Interface.
MRA
R/W
Aliases a Memory Read Command to Memory
Read Multiple Command. This causes PowerSpan
II to prefetch read data on the destination bus
(processor bus or PCI) up to the amount
programmed in the RD_AMT[2:0] field.
Disabled
RD_AMT[2:0]
R/W
Controls the prefetch read amount for a Memory
Read when MRA is enabled. Memory Read
Multiple always causes prefetch up to the value in
RD_AMT[2:0]. This can be programmed up to a
maximum of 128 bytes.
8 bytes is the default
prefetch read amount
PowerSpan II behavior is undefined if more than one overlapping target image claims a
transaction. For example, if two target image have the same base address and size, then they
must have unique master bits set in the
“PCI-1 Target Image x Translation Address Register”
Table 5: Programming Model for PCI Target Image Control Register
Bits
Type
Description
Default Setting