
Chapter 19 Debug Module (DBGV1)
MC9S12HZ256 Data Sheet, Rev. 2.04
Freescale Semiconductor
551
5:4
BKBMB[H:L]
Breakpoint Mask High Byte and Low Byte of Data (Second Address)
— In dual mode, these bits may be
used to mask (disable) the comparison of the high and/or low bytes of the second address breakpoint. The
functionality is as given in
Table 19-17
.
The x:0 case is for a full address compare. When a program page is selected, the full address compare will be
based on bits for a 20-bit compare. The registers used for the compare are {DBGCBX[5:0], DBGCBH[5:0],
DBGCBL[7:0]} where DBGCBX[5:0] corresponds to PPAGE[5:0] or extended address bits [19:14] and CPU
address [13:0]. When a program page is not selected, the full address compare will be based on bits for a 16-bit
compare. The registers used for the compare are {DBGCBH[7:0], DBGCBL[7:0]} which corresponds to CPU
address [15:0].
Note:
This extended address compare scheme causes an aliasing problem in BKP mode in which several
physical addresses may match with a single logical address. This problem may be avoided by using DBG
mode to generate breakpoints.
The 1:0 case is not sensible because it would ignore the high order address and compare the low order and
expansion addresses. Logic forces this case to compare all address lines (effectively ignoring the BKBMBH
control bit).
The 1:1 case is useful for triggering a breakpoint on any access to a particular expansion page. This only makes
sense if a program page is being accessed so that the breakpoint trigger will occur only if DBGCBX compares.
In full mode, these bits may be used to mask (disable) the comparison of the high and/or low bytes of the data
breakpoint. The functionality is as given in
Table 19-18
.
3
RWAEN
Read/Write Comparator A Enable Bit
— The RWAEN bit controls whether read or write comparison is enabled
forcomparator A.See
Section 19.4.2.1.1,“ReadorWriteComparison
,”formoreinformation.Thisbitisnotuseful
for tagged operations.
0 Read/Write is not used in comparison
1 Read/Write is used in comparison
2
RWA
Read/Write Comparator A Value Bit
— The RWA bit controls whether read or write is used in compare for
comparator A. The RWA bit is not used if RWAEN = 0.
0 Write cycle will be matched
1 Read cycle will be matched
1
RWBEN
Read/Write Comparator B Enable Bit
— The RWBEN bit controls whether read or write comparison is enabled
forcomparator B.See
Section 19.4.2.1.1,“ReadorWriteComparison
,”formoreinformation.Thisbitisnotuseful
for tagged operations.
0 Read/Write is not used in comparison
1 Read/Write is used in comparison
0
RWB
Read/Write Comparator B Value Bit
— The RWB bit controls whether read or write is used in compare for
comparator B. The RWB bit is not used if RWBEN = 0.
0 Write cycle will be matched
1 Read cycle will be matched
Note:
RWB and RWBEN are not used in full mode.
Table 19-16. Breakpoint Mask Bits for First Address
BKAMBH:BKAMBL
Address Compare
DBGCAX
Yes
1
Yes
1
Yes
1
DBGCAH
DBGCAL
x:0
0:1
1:1
Full address compare
256 byte address range
16K byte address range
1
If PPAGE is selected.
Yes
Yes
No
Yes
No
No
Table 19-15. DBGC3 Field Descriptions (continued)
Field
Description