Answers Database
LogiCORE PCI: Base Address Register attributes
Record #3549
Product Family: Documentation
Product Line: PCI Apps
Product Part: PCI Frequently Asked Questions
Problem Title:
LogiCORE PCI: Base Address Register attributes
Problem Description:
Urgency: Standard
Problem Description:
What are the attributes of a BAR as defined by the PCI spec?
Solution 1:
The BAR attributes are:
1) Whether the BAR is enabled. Disabling the BAR allows the
optimizations tools to delete the entire circuit.
2) The size of the address space block required. In the
LogiCORE interface, the address space can be as small as 16
bytes, or as large as 2 Gigabytes. For 80x86 systems, the
maximum allowed I/O space is 256 bytes.
3) The ability of memory space (not I/O space) to be prefetched.
4) The location of memory space in total address space. This
can be anywhere in 32-bit address space, anywhere in 64-bit
address space, or below 1 Mbyte. Here are the Type settings
as documented in the PCI Local Bus Specification, Rev. 2.1,
page 196:
TYPE00 - locate anywhere in 32 bit address space
TYPE01 - locate below 1 Meg
TYPE10 - locate anywhere in 64 bit address space
5) Whether the address space is defined as memory or I/O.
The BAR will only respond to commands that access the
specified address space.
End of Record #3549 - Last Modified: 11/04/99 10:58 |
