Window Mask Registers Bit Descriptions

Window Mask Registers (Wx_MASK, x=0-3)

Address: 87.6000.0440, 87.6000.0540, 87.6000.0640, 87.6000.0740
The Window Mask Register (WMR) provides a mask corresponding to bits <31:20> of an incoming PCI address. The size of each window can be programmed to be from 1 MB to 4 GB in powers of two (2) by masking bits of the incoming PCI address through the WMR as shown below.

There are four WMRs: W_MASK[0], W_MASK[1], W_MASK[2], and W_MASK[3]. The W_MASK[x] registers should not be modified unless software ensures that no PCI traffic is targeted for the window being modified.

To determine whether there is a hit in the target window, the incoming PCI address bits <31:20> are compared with the each of the four WBRs; where the W_MASK register determines which bits are involved in the comparison. The Target Window is "Hit" when the masked addresses matches a valid WBR.

W_
MASK

<31:20>
RW

W_MASK specifies the size of the PCI Target Window (see table below) and it is used also to mask out address bits not used when determining a PCI Target Window "hit."

W_MASK <31:20>	Size of Window
0000 0000 0000	1 MB
0000 0000 0001	2 MB
0000 0000 0011	4 MB
0000 0000 0111	8 MB
0000 0000 1111	16 MB
0000 0001 1111	32 MB
0000 0011 1111	64 MB
0000 0111 1111	128 MB
0000 1111 1111	256 MB
0001 1111 1111	512 MB
0011 1111 1111	1 GB
0111 1111 1111	2 GB
1111 1111 1111	4 GB
Otherwise	Not supported

Reserved

<19:0>
RO

N/A