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Cortex-A8 Technical Reference Manual - ARM Information Center

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Watchpoint<br />

address mask<br />

Reserved<br />

Debug<br />

31 29 28 24 23 21 20 19 16 15 14 13 12<br />

5 4 3 2 1 0<br />

E Linked BRP Byte address select L/S SP W<br />

Reserved<br />

Reserved<br />

Secure state access control<br />

Figure 12-13 Watchpoint Control Registers format<br />

Table 12-26 shows how the bit values correspond with the Watchpoint Control Registers<br />

functions.<br />

Bits Field Function<br />

[31:29] - Reserved. RAZ, SBZP.<br />

[28:24] Watchpoint<br />

address mask<br />

[23:21] - Reserved. RAZ, SBZP.<br />

Table 12-26 Watchpoint Control Registers bit functions<br />

Watchpoint address mask. This field is used to watch a range of addresses by masking lower<br />

order address bits out of the watchpoint comparison:<br />

b00000 = no mask<br />

b00001 = reserved<br />

b00010 = reserved<br />

b00011 = 0x00000007 mask for data address<br />

b00100 = 0x0000000F mask for data address<br />

b00101 = 0x0000001F mask for data address<br />

.<br />

.<br />

.<br />

b11111 = 0x7FFFFFFF mask for data address.<br />

Note<br />

• If WCR[28:24] is not set to b00000, then WCR[12:5] must be set to b11111111.<br />

Otherwise, the behavior is Unpredictable.<br />

• If WCR[28:24] is not set to b00000, then the corresponding WVR bits that are not being<br />

included in the comparison Should-Be-Zero. Otherwise, the behavior is Unpredictable.<br />

• To watch for a write to any byte in an 8-byte aligned object of size 8 bytes, <strong>ARM</strong><br />

recommends that a debugger sets WCR[28:24] to b00111, and WCR[12:5] to<br />

b11111111. This is compatible with both <strong>ARM</strong>v7 debug compliant implementations<br />

that have an eight-bit WCR[12:5] and with those that have a four-bit WCR[8:5] byte<br />

address select field.<br />

[20] E Enable linking bit:<br />

0 = linking disabled<br />

1 = linking enabled.<br />

When this bit is set to 1, this watchpoint is linked with the context ID holding BRP selected<br />

by the linked BRP field.<br />

[19:16] Linked BRP Linked BRP number. The binary number encoded here indicates a context ID holding BRP to<br />

link this WRP with. If this WRP is linked to a BRP that is not configured for linked context<br />

ID matching, it is Unpredictable whether a watchpoint debug event is generated.<br />

<strong>ARM</strong> DDI 0344K Copyright © 2006-2010 <strong>ARM</strong> Limited. All rights reserved. 12-31<br />

ID060510 Non-Confidential

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