Example Enhanced Configuration Access
Refer to Figure 20-9 on page 737. The following x86 code sample will cause the Root Complex to perform a read from Bus 4, Device 0, Function 0's Vendor ID configuration register. The example assumes that the 256MB-aligned base address of the Enhanced Configuration memory-mapped IO range is 50000000h:
mov ax,[50400000];memory-mapped IO read
Address bits 63:28 indicates the upper 36 bits of the 256MB-aligned base address of the overall Enhanced Configuration address range (in this case, 000000005h).
Address bits 27:20 select the target bus (in this case, 4).
Address bits 19:15 select the target device (in this case, 0) on the bus.
Address bits 14:12 select the target function (in this case, 0) within the device. ...
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