MPC555
/
MPC556
CENTRAL PROCESSING UNIT
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
3-13
FPSCR[0:12] and FPSCR[21:23] are floating-point exception condition bits. These bits
are sticky, except for the floating-point enabled exception summary (FEX) and float-
ing-point invalid operation exception summary (VX). Once set, sticky bits remain set
until they are cleared by an
mcrfs
,
mtfsfi
,
mtfsf
, or
mtfsb0
instruction.
summarizes which bits in the FPSCR are sticky status bits, which are nor-
mal status bits, and which are control bits.
FEX and VX are the logical ORs of other FPSCR bits. Therefore these two bits are not
listed among the FPSCR bits directly affected by the various instructions.
A listing of FPSCR bit descriptions is shown in
Table 3-4 FPSCR Bit Categories
Bits
Type
[0], [3:12], [21:23]
Status, sticky
[1:2], [13:20]
Status, not sticky
[24:31]
Control
FPSCR
— Floating-Point Status and Control Register
MSB
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
FX
FEX
VX
OX
UX
ZX
XX
VXS-
NAN
VXISI
VXIDI
VXZD
Z
VXIMZ VXVC
FR
FI
FPRF
0
RESET: UNCHANGED
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
LSB
31
FPRF[1:4]
0
VX-
SOFT
VX-
SQRT
VXCVI
VE
OE
UE
ZE
XE
NI
RN
RESET: UNCHANGED
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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