MPC555
/
MPC556
CENTRAL PROCESSING UNIT
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
3-22
The floating-point exception mode bits are interpreted as shown in
3.9.2 DAE/Source Instruction Service Register (DSISR)
The 32-bit DSISR identifies the cause of data access and alignment exceptions.
3.9.3 Data Address Register (DAR)
After an alignment exception, the DAR is set to the effective address of a load or store
element.
28
—
Reserved
29
DC-
MPEN
1
Decompression On/Off
0 = RCPU Normal Operation
1 = RCPU is running in Compressed mode
30
RI
Recoverable exception (for machine check and non-maskable breakpoint exceptions)
0 = Machine state is not recoverable.
1 = Machine state is recoverable.
31 LE
Little-endian mode
0 = Processor operates in big-endian mode during normal processing.
1 = Processor operates in little-endian mode during normal processing.
NOTES:
1. This bit is only available on the MPC556.
Table 3-13 Floating-Point Exception Mode Bits
FE[0:1]
Mode
00
Ignore exceptions mode — Floating-point exceptions do not cause the
floating-point assist error handler to be invoked.
01, 10, 11
Floating-point precise mode — The system floating-point assist error
handler is invoked precisely at the instruction that caused the enabled
exception.
DSISR
— DAE/Source Instruction Service Register
SPR 18
MSB
0
1
2
3
4
5
6
7
8
9
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
LSB
31
DSISR
RESET: UNCHANGED
DAR
— Data Address Register
SPR 19
MSB
0
1
2
3
4
5
6
7
8
9
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
LSB
31
Data Address
RESET: UNCHANGED
Table 3-12 Machine State Register Bit Descriptions (Continued)
Bit(s)
Name
Description
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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