ARM R4F, r1p3 manual Setting a simple aligned watchpoint, Example 11-7 Setting a simple breakpoint

Debug

For a simple breakpoint, you can program the settings for the other control bits as Table 11-43shows:

Table 11-43 Values to write to BCR for a simple breakpoint

Bits	Value to write	Description
[31:29]	0b000	Reserved
[28:24]	0b00000	Breakpoint address mask
[23]	0b0	Reserved
[22:20]	0b000	Meaning of BVR
[19:16]	0b0000	Linked BRP number
[15:9]	0b00	Reserved
[8:5]	Derived from address	Byte address select
[4:3]	0b00	Reserved
[2:1]	0b11	Supervisor access control
[0]	0b1	Breakpoint enable

Example 11-7shows the sequence of instructions for setting a simple breakpoint.

Example 11-7 Setting a simple breakpoint

SetSimpleBreakpoint(int break_num, uint32 address, iset_t isa)

{

//Step 1. Disable the breakpoint being set. WriteDebugRegister(80 + break_num, 0x0);

//Step 2. Write address to the BVR, leaving the bottom 2 bits zero. WriteDebugRegister(64 + break_num, address & 0xFFFFFFC);

//Step 3. Determine the byte address select value to use.

case (isa) of

{

//Note: The processor does not support Jazelle or ThumbEE states,

//but the ARMv7 Debug architecture does

when JAZELLE:

byte_address_select := (1 << (address & 3)); when THUMB:

byte_address_select := (3 << (address & 2)); when ARM:

byte_address_select := 15;

}

//Step 4. Write the mask and control register to enable the breakpoint. breakpoint

WriteDebugRegister(80 + break_num, 7 (byte_address_select << 5));

}

Setting a simple aligned watchpoint

The simplest and most common type of watchpoint watches for a write to a given address in memory. In practice, a data object spans a range of addresses but is aligned to a boundary corresponding to its size, so you must set the byte address select bits in the same way as for a breakpoint.

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