ARM r1p3, R4F manual 45shows some examples, Single-stepping, Not required

Debug

Table 11-45shows some examples.

Table 11-45 Example byte address masks for watchpointed objects

Address of object	Object size	First address	First byte	Second address	Second byte
	in bytes	value	address mask	value	address mask
0x00008000	1	0x00008000	0b00000001	Not required	-
0x00008007	1	0x00008000	0b10000000	Not required	-
0x00009000	2	0x00009000	0b00000011	Not required	-
0x0000900c	2	0x00009000	0b11000000	Not required	-
0x0000900d	2	0x00009000	0b10000000	0x00009008	0b00000001
0x0000A000	4	0x0000A000	0b00001111	Not required	-
0x0000A003	4	0x0000A000	0b01111000	Not required	-
0x0000A005	4	0x0000A000	0b11100000	0x0000A008	0b00000001
0x0000B000	8	0x0000B000	0b11111111	Not required	-
0x0000B001	8	0x0000B000	0b11111110	0x0000B008	0b00000001

Example 11-9shows the code for setting a simple unaligned watchpoint.

Example 11-9 Setting a simple unaligned watchpoint

bool SetSimpleWatchpoint(int watch_num, uint32 address, int size)

{

//Step 1. Disable the watchpoint being set. WriteDebugRegister(112 + watch_num, 0x0);

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

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

byte_address_select := (1 << size) - 1;

byte_address_select := (byte_address_select) << (address & 7);

//Step 4. Write the mask and control register to enable the breakpoint. WriteDebugRegister (112 + watch_num, 5'b23 ((byte_address_select & 0xFF) << 5));

//Step 5. Set second watchpoint if required. This is the case if the byte

//address mask is more than 8 bits.

if (byte_address_select >= 256)

{

WriteDebugRegister(112 + watch_num + 1, 0);

WriteDebugRegister(96 + watch_num + 1, (address & 0xFFFFFF8) + 8); WriteDebugRegister(112 + watch_num + 1 23 ((byte_address_select & 0xFF00) >> 3));

}

//Step 6. Return flag to caller indicating if second watchpoint was used. return (byte_address_select >= 256)

}

11.11.3 Single-stepping

You can use the breakpoint mismatch bit to implement single-stepping on the processor. Unlike high-level stepping, single-stepping implements a low-level step that executes a single instruction at a time. With high-level stepping, the instruction is decoded to determine the address of the next instruction and a breakpoint is set at that address.

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