What are the attributes of a BAR as defined by the PCI specifications?
The BAR attributes are:
1. Whether the BAR is enabled. Disabling the BAR allows the optimization 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 pre-fetched.
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. The Type settings as documented in the PCI Local Bus Specification, Rev. 2.1, page 196 are as follows:
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.