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Cortex-M3 Processor Registers

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2.7.2.19 MASK3 Register (Offset = 54h) [reset = X]

MASK3 is shown in Figure 2-59 and described in Table 2-83.

Mask 3 Use the DWT Mask Registers 3 to apply a mask to data addresses when matching against

COMP3.

Figure 2-59. MASK3 Register

31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0

RESERVED MASK

R/W-X R/W-0h

Table 2-83. MASK3 Register Field Descriptions

Bit Field Type Reset Description

31-4 RESERVED R/W X

Software should not rely on the value of a reserved. Writing any

other value than the reset value may result in undefined behavior.

3-0 MASK R/W 0h

Mask on data address when matching against COMP3. This is the

size of the ignore mask. That is, DWT matching is performed

as:(ADDR ANDed with (0xFFFF left bit-shifted by MASK)) ==

COMP3. However, the actual comparison is slightly more complex to

enable matching an address wherever it appears on a bus. So, if

COMP3 is 3, this matches a word access of 0, because 3 would be

within the word.

114

SWCU117A–February 2015–Revised March 2015

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