MC68HC912B32MFU8 MOTOROLA [Motorola, Inc], MC68HC912B32MFU8 Datasheet - Page 124

• Manufacturer Part Number: MC68HC912B32MFU8
• Description: 16-Bit Microcontroller
• Manufacturer: MOTOROLA [Motorola, Inc]

16.3.2 Registers
BRKCT0 — Breakpoint Control Register 0
BKEN1, BKEN0 — Breakpoint Mode Enable
BKPM — Break on Program Addresses
BK1ALE — Breakpoint 1 Range Control
BK0ALE — Breakpoint 0 Range Control
124
MOTOROLA
RESET:
BKEN1 BKEN0
Breakpoint operation consists of comparing data in the breakpoint address registers (BRKAH/BRKAL)
to the address bus and comparing data in the breakpoint data registers (BRKDH/BRKDL) to the data
bus. The breakpoint data registers can also be compared to the address bus. The scope of comparison
can be expanded by ignoring the least significant byte of address or data matches.
The scope of comparison can be limited to program data only by setting the BKPM bit in breakpoint con-
trol register 0.
To trace program flow, setting the BKPM bit causes address comparison of program data only. Control
bits are also available that allow checking read/write matches.
Read and write anytime.
This register is used to control the breakpoint logic.
This bit controls whether the breakpoint will cause a break on a match (next instruction boundary) or on
a match that will be an executable opcode. Data and unexecuted opcodes cannot cause a break if this
bit is set. This bit has no meaning in SWI dual address mode. The SWI mode only performs program
breakpoints.
Only valid in dual address mode.
Valid in all modes.
0
0
1
1
• Breakpoints are not allowed if the BDM mode is already active. Active mode means the CPU is
• BDM should not be entered from a breakpoint unless the ENABLE bit is set in the BDM. This is
0 = On match, break at the next instruction boundary
1 = On match, break if the match is an instruction that will be executed. This uses tagging as its
0 = BRKDL will not be used to compare to the address bus.
1 = BRKDL will be used to compare to the address bus.
0 = BRKAL will not be used to compare to the address bus.
1 = BRKAL will be used to compare to the address bus.
executing out of the BDM ROM.
important because even if the ENABLE bit in the BDM is negated the CPU actually does execute
the BDM ROM code. It checks the ENABLE and returns if not set. If the BDM is not serviced by
the monitor then the breakpoint would be re-asserted when the BDM returns to normal CPU flow.
There is no hardware to enforce restriction of breakpoint operation if the BDM is not enabled.
breakpoint mechanism.
BKEN1
Bit 7
0
1
0
1
0
Breakpoints Off
SWI — Dual Address Mode
BDM — Full Breakpoint Mode
BDM — Dual Address Mode
BKEN0
6
0
Mode Selected
BKPM
Table 47 Breakpoint Mode Control
5
0
4
0
0
BRKAH/L Usage BRKDH/L Usage
Address Match
Address Match
Address Match
BK1ALE
3
0
—
BK0ALE
2
0
Address Match
Address Match
Data Match
—
1
0
0
MC68HC912B32TS/D
Bit 0
R/W
Yes
Yes
No
MC68HC912B32
—
0
0
Range
Yes
Yes
Yes
—
$0020