System Development and Debugging
MPC885 PowerQUICC Family Reference Manual, Rev. 2
53-12
Freescale Semiconductor
Figure 53-3. Load/Store Support General Structure
Each of the two load/store data comparators (G and H) is 32 bits wide and can be programmed to treat
numbers as signed or unsigned. Each data comparator operates as four independent byte comparators.
Each byte comparator has a mask bit and generates two output signals—equal and less than (if the mask
bit is not set.) Therefore, each 32-bit comparator has eight output signals. These signals generate the equal
and less-than signals according to the compare size programmed by the user (byte, half-word, word). All
signals are significant in byte mode. In half-word mode, only four signals from each 32-bit comparator are
significant; when operating in word mode, only two signals are significant.
One of the next four match events is generated by the equal and less-than signals—equal, not equal, greater
than, or less than, depending on the compare type programmed. Therefore, from the two 32-bit
comparators, eight match indications are generated—Gmatch[0–3] and Hmatch[0–3]. According to the
lower bits of the address and the size of the cycle, only match indications detected on bytes with valid
information are validated. The rest are negated. If the executed cycle has a smaller size than the compare
size (a byte access when the compare size is word or half-word), no match indication is asserted. The
match indication signals generate four load/store data events as shown in
Table 53-7
.
Comparator G
Byte 0
Eq
Lt
Compare
Compare
Ad
d(
30
:3
1
)
Data
Compa
re
V
a
lid
0
V
a
lid
1
V
a
lid
2
V
a
lid
3
G
H
(G&H)
(G|H)
In
s
tr
u
c
tio
n
L-watchpoint 0
L-watchpoint 1
L-breakpoint
Size
Logic
Compare
Byte
Qualifier
Logic
E
v
e
n
ts
G
e
n
e
ra
to
r
AND-OR Logic
Cont
ro
l Bi
ts
E
F
(E
&
F
)
(E
|
F
)
Comparator E
Type Logic
Events
Generator
Lt
Eq
Comparator F
Type Logic
Lt
Eq
Compare
Type
Logic
Byte Mask
Byte 1
Byte 2
Byte 3
Eq
Lt
Eq
Lt
Eq
Lt
Eq
Lt
Eq
Lt
Eq
Lt
Eq
Lt
Size
Type
Comparator H
Byte 0
Eq
Lt
Size
Logic
Compare
Byte
Qualifier
Logic
Type
Logic
Byte Mask
Byte 1
Byte 2
Byte 3
Eq
Lt
Eq
Lt
Eq
Lt
Eq
Lt
Eq
Lt
Eq
Lt
Eq
Lt
Type
Cycle Size
W
a
tc
h
poi
nt
s
Si
ze
Summary of Contents for PowerQUICC MPC870
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Page 1312: ...Byte Ordering MPC885 PowerQUICC Family Reference Manual Rev 2 A 8 Freescale Semiconductor ...
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Page 1370: ...MPC880 MPC885 PowerQUICC Family Reference Manual Rev 2 E 4 Freescale Semiconductor ...
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