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bc (SDM)

Clears one or all previously set hardware or software breakpoints. Use this command to remove breakpoints set with the bs command.

bc [address]


The address of a specific breakpoint to clear. If you don't specify an address, the bc command clears all breakpoints. Use the linear or I/O address of a previously set breakpoint. Physical addresses are not allowed.


This command clears both hardware and software breakpoints. When clearing a hardware breakpoint, it immediately updates the debug registers of the CPU. If you clear all breakpoints, bc does not display any information. If you clear a single breakpoint by specifying its address, bc displays the reason code assigned to that breakpoint when it was set. The reason code is a 32-bit hexadecimal number in the range of 200h-203h for hardware breakpoints or 1000h-101Fh for software breakpoints.

This command returns no output if you try to clear a single breakpoint using a valid address that is not a breakpoint address. No breakpoints are cleared.

Clearing Redundant Breakpoints

You cannot set multiple software breakpoints at the same address. However, if you have set more than one hardware breakpoint at the same address you must clear each individually, or clear all breakpoints. Hardware breakpoints at the same address are cleared from lowest to highest numbered reason code.

To individually clear hardware and software breakpoints set at the same address, issue a bc address command for each breakpoint. SDM clears the software breakpoint on the first command and clears the hardware breakpoint on the second.


Suppose you have set a software breakpoint and a hardware breakpoint at the same address. When you display breakpoints with the bs command, those breakpoints might be listed as follows:
00000203 h 0000104e m b
00001000 s 0000104e

The first breakpoint is a hardware modify breakpoint with reason code 203H. The second is a software execution breakpoint with reason code 1000H. To clear the hardware breakpoint, you must first clear the software breakpoint.

When you issue the bc command for this address, SDM clears the software breakpoint and returns the reason code followed by the prompt (..):

..bc 104e l

When you issue a second bc command for this address, SDM clears the hardware breakpoint:

..bc 104e l

See Also

Debugging tools, System Debug Monitor (SDM), bs