Altera PCI Compiler - Manual (Page 262)

6–12 User Guide Version 11.1 Altera Corporation
PCI Compiler October 2011
PCI Configuration
if the address matches one of the BARs. The PCI-Avalon bridge then
translates the PCI address into an Avalon-MM address before it initiates
the equivalent transaction on the interconnect. The PCI BAR settings in
the PCI Compiler wizard are used to set the appropriate options for the
PCI BAR, so the transactions from PCI can accurately flow to the
interconnect.
For each BAR you must set the following options:
■ BAR Type
■ BAR Size
■ Avalon Base Address
■ Hardwired PCI Address
The following sections explain how to select the appropriate settings for
each option.
BAR Type —The PCI-Avalon bridge supports three BAR types:
■ 32-Bit Prefetchable Memory: This type of BAR is typical for most
systems. It is used for Avalon-MM I/O. Implementing at least one
32-bit prefetchable BAR enables a prefetchable master port for the
PCI-Avalon bridge—except if you select the Single-Cycle Transfers
Only performance profile. This enables both burst and single cycle
access to Avalon-MM peripherals for both read and write
transactions.
You can use this option for all types of Avalon-MM peripherals
except those that do not support prefetchable read transactions.
Peripherals that support prefetchable read transactions do not
modify the state of the data when a read operation is performed. A
RAM or ROM is a typical example of a prefetchable peripheral.
Peripherals where a read operation changes the state of the data,
such as a FIFO buffer or a clear-on read register, are called
non-prefetchable and should not be accessed by a prefetchable base
address register.
■ 64-Bit Prefetchable Memory: This BAR is similar to the 32-bit
prefetchable memory BAR except that it supports 64-bit PCI
addressing. This option is only available if you select 64 Bit PCI Bus
in the System Options - 2 tab. The requirement for your device to
support 64-bit addressing is usually apparent from your system
architecture and is driven by the amount of system memory. Because
the Avalon-MM address space can only support 32-bit addresses,
you are limited to the amount of address space that you can reserve