ARM R4 Setting a simple unaligned watchpoint, Example 11-8 Setting a simple aligned watchpoint

Debug

For a simple watchpoint, you can program the settings for the other control bits as Table 11-44shows:

Table 11-44 Values to write to WCR for a simple watchpoint

Bits	Value to write	Description
[31:29]	0b000	Reserved
[28:24]	0b00000	Watchpoint address mask
[23:21]	0b000	Reserved
[20]	0b0	Enable linking
[19:16]	0b0000	Linked BRP number
[15:13]	0b00	Reserved
[12:5]	Derived from address	Byte address select
[4:3]	0b10	Load/Store access control
[2:1]	0b11	Privileged access control
[0]	0b1	Watchpoint enable

Example 11-8shows the code for setting a simple aligned watchpoint.

Example 11-8 Setting a simple aligned watchpoint

SetSimpleAlignedWatchpoint(int watch_num, uint32 address, int size)

{

//Step 1. Disable the watchpoint being set. WriteDebugRegister(112 + watch_num, 0);

//(Step 2. Write address to the WVR, leaving the bottom 3 bits zero. WriteDebugRegister(96 + watch_num, address & 0xFFFFFF8);

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

case (size) of

{

when 1:

byte_address_select := (1 << (address & 7)); when 2:

byte_address_select := (3 << (address & 6)); when 4:

byte_address_select := (15 << (address & 4)); when 8:

byte_address_select := 255;

}

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

WriteDebugRegister(112 + watch_num, 23 (byte_address_select << 5));

}

Setting a simple unaligned watchpoint

Using the byte address select bits, certain unaligned objects up to a doubleword (64 bits) can be watched in a single watchpoint. However, this cannot cover all cases, and in many cases a second watchpoint might be required.

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