Debug
ARM DDI 0500D
Copyright © 2013-2014 ARM. All rights reserved.
11-10
ID021414
Non-Confidential
To access the DBGBCR
n
_EL1 in AArch64 Execution state, read or write the register with:
MRS <Xt>, DBGBCR
n
_EL1; Read Debug Breakpoint Control Register
n
MSR DBGBCR
n
_EL1, <Xt>; Write Debug Breakpoint Control Register
n
To access the DBGBCR
n
in AArch32 Execution state, read or write the CP14 register with:
MRC p14, 0, <Rt>, c0, cn, 4; Read Debug Breakpoint Control Register
n
MCR p14, 0, <Rt>, c0, cn, 4; Write Debug Breakpoint Control Register
n
The DBGBCR
n
_EL1 can be accessed through the internal memory-mapped interface and the
external debug interface, offset
0x4n8
.
[8:5]
BAS
a
Byte Address Select. Defines which half-words a regular breakpoint matches, regardless of the instruction set and
execution state. A debugger must program this field as follows:
0x3
Match the T32 instruction at DBGBVRn.
0xC
Match the T32 instruction at 2.
0xF
Match the A64 or A32 instruction at DBGBVRn, or context match.
All other values are reserved.
Note
The ARMv8-A architecture does not support direct execution of Java bytecodes. BAS[3] and BAS[1] ignore
writes and on reads return the values of BAS[2] and BAS[0] respectively.
[4:3]
-
Reserved,
RES
0.
[2:1]
PMC
Privileged Mode Control. Determines the exception level or levels that a breakpoint debug event for breakpoint
n
is generated.
This field must be interpreted with the SSC and HMC fields to determine the mode and security states that can be
tested.
See the
ARM
®
Architecture Reference Manual ARMv8, for ARMv8-A architecture profile
for possible values of
the fields.
Note
Bits[2:1] have no effect for accesses made in Hyp mode.
[0]
E
Enable breakpoint. This bit enables the BRP:
0
BRP disabled.
1
BRP enabled.
A BRP never generates a breakpoint debug event when it is disabled.
Note
The value of DBGBCR.E is
UNKNOWN
on reset. A debugger must ensure that DBGBCR.E has a defined value
before it programs DBGDSCR.MDBGen and DBGDSCR.HDBGen to enable debug.
a. See the
ARM
®
Architecture Reference Manual ARMv8, for ARMv8-A architecture profile
for more information on how the BAS field is
interpreted by hardware.
Table 11-4 DBGBCR
n
_EL1 bit assignments (continued)
Bits
Name
Function