ARM Architecture Reference Manual ARMv7-A and ARMv7-R edition

Linked comparisons
Debug Registers Reference
For linked comparisons, a comparison includes a Context ID match, defined by a BRP, with one or more
address comparisons defined by other BRPs or WRPs linked to the Context ID match:
Zero or more other BRPs, each programmed to define a linked IVA match.
Zero or more other BRPs, each programmed to define a linked IVA mismatch.
Note
Linked IVA mismatch is not supported in v6 Debug.
Zero or more WRPs, each programmed to define a linked DVA match.
The Breakpoint or Watchpoint debug event is generated only if both:
the Context ID match is true
the IVA match or mismatch, or the DVA match, is true.
In this description:
BRPm is used to define the Context ID match.
BRPn is configured to define a linked IVA match or mismatch, and is linked to BRPm
WRPn is configured to define a linked DVA match, and is linked to BRPm
If there are no BRPs and no WRPs linked to BRPm then BRPm cannot generate any debug events. The rest
of this description assumes at least one BRP or WRP is linked to BRPm.
To configure BRPm to define the Context ID match part of the linked Context ID matches:
program DBGBVRm[31:0] with the Context ID to be matched
program DBGBCRm[22:20] to 0b011, linked Context ID comparison
generation of the debug events is UNPREDICTABLE unless all of these conditions are met:
— DBGBCRm[19:16] is programmed to 0b0000
— DBGBCRm[15:14] is programmed to 0b00
— DBGBCRm[8:5] is programmed to 0b1111
— DBGBCRm[2:1] is programmed to 0b11.
To configure BRPn to define the IVA match or mismatch part of a linked Context ID match:
program DBGBVRn[31:2] with the address for comparison, and DBGBVRn[1:0] to b00
program DBGBCRn[22:20] to either:
— 0b001, for linked IVA match
— 0b101, for linked IVA mismatch, in v6.1 Debug or v7 Debug
program DBGBCRn[19:16] to m, the number of the BRP that defines the Context ID match
if required, program DBGBCRn[15:14,2:1] to include the state of the processor in the comparison.
To configure WRPn to define the DVA match part of a linked Context ID match:
program DBGWVRn[31:2] with the address for comparison, and DBGWVRn[1:0] to b00
program DBGWCRn[20] to 1, to enable linking
program DBGWCRn[19:16] to m, the number of the BRP that defines the Context ID match
if required, program DBGWCRn[15:14,2:1] to include the state of the processor in the comparison.
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