ARM r1p3, R4F manual Watchpoint Control Registers format, Watchpoint Control Registers functions

Debug

31	29 28			24 23	21 20 19				16 15 14 13 12			5	4	3 2	1	0
			Watchpoint				E	Linked BRP			Byte address select		L/S		SP	W
			address mask
		Reserved				Reserved					Reserved
										Secure state access control

Figure 11-11 Watchpoint Control Registers format

Table 11-20shows how the bit values correspond with the Watchpoint Control Registers functions.

			Table 11-20 Watchpoint Control Registers functions
Bits	Field	Function
[31:29]	Reserved	Do not modify on writes. On reads, the value returns zero.
[28:24]	Watchpoint	This field watches a range of addresses by masking lower order address bits out of the
	address	watchpoint comparison.
	mask	b00000	= no mask
		b00001 = Reserved
		b00010 = Reserved
		b00011 = 0x00000007 mask for data address
		b00100	= 0x0000000F mask for data address
		b00101	= 0x0000001F mask for data address
		...

b11111 = 0x7FFFFFFF mask for data address.

Note

•If WCR[28:24] is not set to b00000, then WCR[12:5] must be set to b11111111. Otherwise the behavior is Unpredictable.

•If WCR[28:24] is not set to b00000, then the corresponding WVR bits that are not being included in the comparison Should Be Zero. Otherwise the behavior is Unpredictable.

•To watch for a write to any byte in an 8-byte aligned object of size 8 bytes, ARM recommends that a debugger sets WCR[28:24] to b00111, and WCR[12:5] to b11111111. This is compatible with both ARMv7 debug compliant implementations that have an

8-bit WCR[12:5] and with those that have a 4-bit WCR[8:5] byte address select field.

[23:21]	Reserved	Do not modify on writes. On reads, the value returns zero.
[20]	E	Enable linking bit:
		0 = linking disabled
		1 = linking enabled.
		When this bit is set, this watchpoint is linked with the context ID holding BRP selected by the
		linked BRP field.
[19:16]	Linked	Linked BRP number. The binary number encoded here indicates a context ID holding BRP to
	BRP	link this WRP with. If this WRP is linked to a BRP that is not configured for linked context ID
		matching, it is Unpredictable whether a watchpoint debug event is generated.
[15:14]	Secure state	RAZ or SBZP.
	access
	control
[13]	Reserved	Appear as zero when read. Do not modify on writes.

ARM DDI 0363E	Copyright © 2009 ARM Limited. All rights reserved.	11-27
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