E-6
MPC8240 Integrated Processor User’s Manual
PowerPC Register Set
E.1.1.4 Floating-Point Status and Control Register (FPSCR)
The FPSCR is shown in Figure E-5.
Figure E-5. Floating-Point Status and Control Register (FPSCR)
A listing of FPSCR bit settings is shown in Table E-4.
Table E-4. FPSCR Bit Settings
Bit(s)
Name
Description
0
FX
Floating-point exception summary. Every floating-point instruction, except mtfsfi and mtfsf,
implicitly sets FPSCR[FX] if that instruction causes any of the floating-point exception bits in the
FPSCR to transition from 0 to 1. The mcrfs, mtfsfi, mtfsf, mtfsb0, and mtfsb1 instructions can
alter FPSCR[FX] explicitly. This is a sticky bit.
1
FEX
Floating-point enabled exception summary. This bit signals the occurrence of any of the
enabled exception conditions. It is the logical OR of all the floating-point exception bits masked
by their respective enable bits (FEX = (VX & VE) ^ (OX & OE) ^ (UX & UE) ^ (ZX & ZE) ^ (XX &
XE)). The mcrfs, mtfsf, mtfsfi, mtfsb0, and mtfsb1 instructions cannot alter FPSCR[FEX]
explicitly. This is not a sticky bit.
2
VX
Floating-point invalid operation exception summary. This bit signals the occurrence of any
invalid operation exception. It is the logical OR of all of the invalid operation exceptions. The
mcrfs, mtfsf, mtfsfi, mtfsb0, and mtfsb1 instructions cannot alter FPSCR[VX] explicitly. This
is not a sticky bit.
3
OX
Floating-point overflow exception. This is a sticky bit.
4
UX
Floating-point underflow exception. This is a sticky bit.
5
ZX
Floating-point zero divide exception. This is a sticky bit.
6
XX
Floating-point inexact exception. This is a sticky bit.
FPSCR[XX] is the sticky version of FPSCR[FI]. The following rules describe how FPSCR[XX] is
set by a given instruction:
• If the instruction affects FPSCR[FI], the new value of FPSCR[XX] is obtained by logically
ORing the old value of FPSCR[XX] with the new value of FPSCR[FI].
• If the instruction does not affect FPSCR[FI], the value of FPSCR[XX] is unchanged.
7
VXSNAN
Floating-point invalid operation exception for SNaN. This is a sticky bit.
8
VXISI
Floating-point invalid operation exception for
∞
–
∞
. This is a sticky bit.
9
VXIDI
Floating-point invalid operation exception for
∞
÷
∞
. This is a sticky bit.
10
VXZDZ
Floating-point invalid operation exception for 0 ÷ 0. This is a sticky bit.
11
VXIMZ
Floating-point invalid operation exception for
∞
* 0. This is a sticky bit.
12
VXVC
Floating-point invalid operation exception for invalid compare. This is a sticky bit.
13
FR
Floating-point fraction rounded. The last arithmetic or rounding and conversion instruction that
rounded the intermediate result incremented the fraction. This bit is not sticky.
0
1
2
3
4
5
6
7
8
9
10 11
12 13 14 15
19 20 21 22 23 24 25 26 27 28 29 30
31
VXIDI
VXISI
VXSNAN
VXZDZ
VXIMZ
VXVC
VXSOFT
VXSQRT
VXCVI
Reserved
FX FEX VX OX UX ZX XX
FR FI
FPRF
0 VE OE UE ZE XE NI
RN
Summary of Contents for MPC8240
Page 1: ...MPC8240UM D Rev 1 1 2001 MPC8240 Integrated Processor User s Manual ...
Page 38: ...xviii MPC8240 Integrated Processor User s Manual TABLES Table Number Title Page Number ...
Page 48: ...xlviii MPC8240 Integrated Processor User s Manual Acronyms and Abbreviations ...
Page 312: ...6 94 MPC8240 Integrated Processor User s Manual ROM Flash Interface Operation ...
Page 348: ...7 36 MPC8240 Integrated Processor User s Manual PCI Host and Agent Modes ...
Page 372: ...8 24 MPC8240 Integrated Processor User s Manual DMA Register Descriptions ...
Page 394: ...9 22 MPC8240 Integrated Processor User s Manual I2O Interface ...
Page 412: ...10 18 MPC8240 Integrated Processor User s Manual Programming Guidelines ...
Page 454: ...12 14 MPC8240 Integrated Processor User s Manual Internal Arbitration ...
Page 466: ...13 12 MPC8240 Integrated Processor User s Manual Exception Latencies ...
Page 516: ...16 14 Watchpoint Trigger Applications ...
Page 538: ...B 16 MPC8240 Integrated Processor User s Manual Setting the Endian Mode of Operation ...
Page 546: ...C 8 MPC8240 Integrated Processor User s Manual ...
Page 640: ...INDEX Index 16 MPC8240 Integrated Processor User s Manual ...