Mc68851 Breakpoint Architecture; Figure 4-5. Breakpoint Registers; Figure 4-6. Breakpoint Acknowledge Data Register Format; Figure 4-7. Breakpoint Acknowledge Control Register Format - Motorola MVME135 User Manual

FUNCTIONAL DESCRI PTION
4.10.3 MC68851 Breakpoi nt Archi tecture
For each of the eight breakpoint opcodes recognized by the MC68020,
the MC68851 has a pair of registers: a breakpoint acknowledge
control register and a breakpoint acknowledge data register. Figure
4-5 illustrates these and the breakpoint opcode to which each pair
corresponds.
15
o
15
o
CORRESPONDING
OPCODE
BAOO BACO
S4848
BADI BAC1
$4849
BAD2 BAC2
S464A
BAD3
BACl
$484B
BAD4 BAC4
$484C
BADS
BACS
$4SCO
BAD6 BACS
S4ME
BAD7
BAC7
S484f
FIGURE 4-5. BREAKPOINT REGISTERS
Each of the breakpoint acknowledge data registers, BAD0 through
BAD7, can be loaded with a replacement opcode for transfer to the
MC68020 during the MC68851 acknowledge cycle. Using the PMOVE
instruction, the 16-bit value for a legal MC68020 opcode may be
written to (or read from) any BADx register in the format
illustrated in Figure 4-6.
15
BAD.
REPLACEMENT
OPCOOE
FIGURE 4-6. BREAKPOINT ACKNOWLEDGE DATA REGISTER FORMAT
The manner in which the data in
controlled by data written
acknowledge control register -
Figure 4-7.
a BAD x register is actually used is
in the corresponding breakpoint
BACx- in the format illustrated in
15 7
o
BAC.
I
BPE
I
0
I
0
I
0
I
0
I
0 0
I
0
I
FIGURE 4-7. BREAKPOINT ACKNOWLEDGE CONTROL REGISTER FORMAT
4-11
I