MPC555
/
MPC556
CENTRAL PROCESSING UNIT
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
3-47
3.15.4.9 Floating-Point Unavailable Interrupt
The floating-point unavailable interrupt is generated by the MPC555 / MPC556 core
as defined in the
OEA
.
3.15.4.10 Trace Interrupt
A trace interrupt occurs if MSR
SE
= 1 and any instruction except
rfi
is successfully com-
pleted or MSR
BE
= 1 and a branch is completed. Notice that the trace interrupt does
not occur after an instruction that caused an interrupt (for instance,
sc
). A monitor/de-
bugger software must change the vectors of other possible interrupt addresses to sin-
gle-step such instructions. If this is unacceptable, other debug features can be used.
Refer to
SECTION 21 DEVELOPMENT SUPPORT
for more information. The follow-
ing registers are set:
Execution resumes at offset 0x00D00 from the base address indicated by MSR
IP
.
3.15.4.11 Floating-Point Assist Interrupt
A floating-point assist interrupt occurs in the following cases:
• When a floating-point exception condition is detected, the corresponding floating-
point enable bit in the FPSCR (floating-point status and control register) is set (ex-
ception enabled) and ((MSR
FE0
| MSR
FE1
) = 1). Note that when ((MSR
FE0
|
MSR
FE1
) and FPSCR
FEX
) is set as a result of move to FPSCR, move to MSR or
rfi
, the floating-point assist interrupt handler is not invoked.
• When an intermediate result is detected and the floating-point underflow excep-
tion is disabled (FPSCR
UE
= 0)
• In some cases when at least one of the source operands is denormalized.
The following registers are set:
Execution resumes at offset 0x00E00 from the base address indicated by MSR
IP.
Register Name
Bits
Description
Save/Restore Register 0 (SRR0)
Set to the effective address of the instruction following the ex-
ecuted instruction
Save/Restore Register 1 (SRR1)
1:4
Set to 0
10:15
Set to 0
Other
Loaded from bits 16:31 of MSR. In the current implementa-
tion, Bit 30 of the SRR1 is never cleared, except by loading a
zero value from MSR
RI
Machine State Register (MSR)
IP
No change
ME
No change
LE
Bit is copied from ILE
Other
Set to 0
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Freescale Semiconductor, Inc.
For More Information On This Product,
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