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Cortex-A8 Technical Reference Manual - ARM Information Center

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12.4.12 Debug Run Control Register<br />

12.4.13 Breakpoint Value Registers<br />

The DRCR requests the processor to enter or leave debug state. It also clears the sticky<br />

exception bits present in the DSCR to 0.<br />

Figure 12-11 shows the bit arrangement of the DRCR.<br />

Debug<br />

Figure 12-11 Debug Run Control Register format<br />

Table 12-21 shows how the bit values correspond with the Debug Run Control Register<br />

functions.<br />

Bits Field Function<br />

31 4 3 2 1 0<br />

[31:4] - Reserved. RAZ, SBZP.<br />

[3] Clear sticky<br />

pipeline advance<br />

[2] Clear sticky<br />

exceptions<br />

Reserved<br />

The BVRs are registers 64-79, at offsets 0x100-0x13C. Each BVR is associated with a Breakpoint<br />

Control Register (BCR), for example:<br />

• BVR0 with BCR0<br />

• BVR1 with BCR1.<br />

This pattern continues up to BVR15 with BCR15.<br />

Clear sticky pipeline advance<br />

Clear sticky exceptions<br />

Restart request<br />

Halt request<br />

Table 12-21 Debug Run Control Register bit functions<br />

Clear sticky pipeline advance. Writing a 1 to this bit clears DSCR[25] to 0.<br />

Clear sticky exceptions. Writing a 1 to this bit clears DSCR[8:6] to b000.<br />

[1] Restart request Restart request. Writing a 1 to this bit requests that the processor leaves debug state. This<br />

request is held until the processor exits debug state. The debugger must poll DSCR[1] to<br />

determine when this request succeeds. This bit always reads as zero. Writes are ignored<br />

when the processor is not in debug state.<br />

[0] Halt request Halt request. Writing a 1 to this bit triggers a halting debug event, that is, a request that the<br />

processor enters debug state. This request is held until the debug state entry occurs. The<br />

debugger must poll DSCR[0] to determine when this request succeeds. This bit always<br />

reads as zero. Writes are ignored when the processor is already in debug state.<br />

A pair of breakpoint registers, BVRn and BCRn, is called a Breakpoint Register Pair (BRPn).<br />

The breakpoint value contained in this register corresponds to either an Instruction Virtual<br />

Address (IVA) or a context ID. Breakpoints can be set on:<br />

• an IVA<br />

• a context ID value<br />

• an IVA and context ID pair.<br />

<strong>ARM</strong> DDI 0344K Copyright © 2006-2010 <strong>ARM</strong> Limited. All rights reserved. 12-26<br />

ID060510 Non-Confidential

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