Central Processing Unit
MPC561/MPC563 Reference Manual, Rev. 1.2
Freescale Semiconductor
3-55
possible interrupt addresses to single-step such instructions. If this is unacceptable, other debug features
can be used. Refer to
Chapter 23, “Development Support
,” for more information. See
for Trace
Exception register settings.
Execution resumes at offset 0x0D00 from the base address indicated by MSR[IP].
3.15.4.12 Floating-Point Assist Exception (0x0E00)
A floating point assist exception occurs when the following conditions are true:
•
A floating-point enabled exception condition is detected;
•
The corresponding floating-point enable bit in the FPSCR (floating point status and control
register) is set (exception enabled); and
•
MSR[FE0] | MSR[FE1] = 1
These conditions are summarized in the following equation:
(MSR[FE0] | MSR[FE1]) AND FPSCR[FEX] = 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, a program exception is generated, rather than a floating-point assist exception.
A floating point assist exception also occurs when a tiny result is detected and the floating point underflow
exception is disabled (FPSCR[UE] = 0).
The register settings for floating-point assist exceptions are shown in
Table 3-32. Register Settings following a Trace Exception
Register Name
Bits
Description
Save/Restore Register 0 (SRR0)
1
1
If the exception occurs during an instruction fetch in Decompression On mode, the SRR0 register will contain a
compressed address.
All
Set to the effective address of the instruction following the
executed instruction
Save/Restore Register 1 (SRR1)
1:4
Cleared to 0
10:15
Cleared to 0
Other
Loaded from bits [16:31] of MSR. In the current
implementation, 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
DCMPEN
This bit is set according to (BBCMCR[EN_COMP] AND
BBCMCR[EXC_COMP])
Other
Cleared to 0
Table 3-33. Register Settings following Floating-Point Assist Exceptions
Register Name
Bits
Description
Save/Restore Register 0 (SRR0)
1
All
Set to the effective address of the instruction that caused the
interrupt
Summary of Contents for MPC561
Page 84: ...MPC561 MPC563 Reference Manual Rev 1 2 lxxxiv Freescale Semiconductor...
Page 144: ...Signal Descriptions MPC561 MPC563 Reference Manual Rev 1 2 2 46 Freescale Semiconductor...
Page 206: ...Central Processing Unit MPC561 MPC563 Reference Manual Rev 1 2 3 62 Freescale Semiconductor...
Page 302: ...Reset MPC561 MPC563 Reference Manual Rev 1 2 7 14 Freescale Semiconductor...
Page 854: ...Time Processor Unit 3 MPC561 MPC563 Reference Manual Rev 1 2 19 24 Freescale Semiconductor...
Page 968: ...Development Support MPC561 MPC563 Reference Manual Rev 1 2 23 54 Freescale Semiconductor...
Page 1144: ...Internal Memory Map MPC561 MPC563 Reference Manual Rev 1 2 B 34 Freescale Semiconductor...
Page 1212: ...TPU3 ROM Functions MPC561 MPC563 Reference Manual Rev 1 2 D 60 Freescale Semiconductor...
Page 1216: ...Memory Access Timing MPC561 MPC563 Reference Manual Rev 1 2 E 4 Freescale Semiconductor...