
Register Model
e200z3 Power Architecture Core Reference Manual, Rev. 2
Freescale Semiconductor
2-15
2.6.2
Count Register (CTR)
CTR can be used to hold a loop count that can be decremented and tested during execution of branch
instructions that contain an appropriately encoded BO field. If the CTR value is 0 before it is decremented,
it is –1 afterward. The entire CTR can hold the branch target address for a Branch Conditional to CTR
(bcctrx) instruction.
2.6.3
Link Register (LR)
The link register, shown in
, provides the branch target address for the branch conditional to LR
instructions, and it holds the return address after branch and link instructions.
CR
n[1]
4 * cr0 + gt
(or
gt
)
4 * cr1 + gt
4 * cr2 + gt
4 * cr3 + gt
4 * cr4
+ gt
4 * cr5
+ gt
4 * cr6
+ gt
4 * cr7
+ gt
33
37
41
45
49
53
57
61
000
001
010
011
100
101
110
111
01
Greater than (GT).
For integer compare instructions:
rA > SIMM or rB (signed comparison) or
r
A > UIMM
or
r
B (unsigned comparison).
CR
n[2]
4 * cr0 + eq
(or
eq
)
4 * cr1 + eq
4 * cr2 + eq
4 * cr3 + eq
4 * cr4
+ eq
4 * cr5
+ eq
4 * cr6
+ eq
4 * cr7
+ eq
34
38
42
46
50
54
58
62
000
001
010
011
100
101
110
111
10
Equal (EQ).
For integer compare instructions:
r
A = SIMM, UIMM,
or
r
B.
CR
n[3]
4 * cr0 + so
(or
so
)
4 * cr1 + so
4 * cr2 + so
4 * cr3 + so
4 * cr4
+ so
4 * cr5
+ so
4 * cr6
+ so
4 * cr7
+ so
35
39
43
47
51
55
59
63
000
001
010
011
100
101
110
111
11
Summary overflow (SO).
For integer compare instructions, this is a copy of
XER[SO] at instruction completion.
32
63
Field
Count value
Reset
Undefined on
m_por assertion, unchanged on p_reset_b
assertion
R/W
R/W
SPR
SPR 9
Figure 2-8. Count Register (CTR)
Table 2-8. CR Setting for Compare Instructions (continued)
CR
n
Bit
Bit Expression
CR Bits
BI
Description
Book E
0–2
3–4
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