User`s guide

The XMI
2.4.2.2 Mask Field
The Mask field is XMI D<47:32> L. The Mask field supplies byte-level
mask information for the XMI Write Mask and Unlock Write Mask
transactions. During nonwrite transactions this field is a "don’t care,"
but proper parity is still generated. (See Figure 2–9.)
The maximum length of a write transaction other than a Disown Write
is one octaword. Disown Writes are always hexword writes. Octaword
writes require 16 mask bits in the upper longword of the command. The
mask bits define which bytes of the following write data cycles are to be
written to the specified locations. For longword- and quadword-length
writes, the unused mask bits (D<47:36> L and D<47:40> L, respectively)
are unspecified and are ignored by responders, other than to check parity.
Figure 2–9 Mask Field Bit Assignments
47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32
9876543210
First QW
63 0
0
15 14 13 12 11 10
b1 b0
b7 b6 b5 b4 b3 b2 b1 b0
Second QW
(if octaword transaction)
b7 b6 b5 b4 b3 b2
msb−p171−89
63
2–25