MPC555
/
MPC556
CENTRAL PROCESSING UNIT
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
3-43
3.14.4.1 Enforce In-Order Execution of I/O (
eieio
) Instruction
When executing an
eieio
instruction, the load/store unit will wait until all previous ac-
cesses have terminated before issuing cycles associated with load/store instructions
following the
eieio
instruction.
3.14.5 Timebase
A description of the timebase register may be found in
and in
SECTION 8 CLOCKS AND POWER CON-
3.15 POWERPC Operating Environment Architecture (OEA)
The MPC555 / MPC556 has an internal memory space that includes memory-mapped
control registers and internal memory used by various modules on the chip. This mem-
ory is part of the main memory as seen by the MPC555 / MPC556 but cannot be ac-
cessed by any external system master.
3.15.1 Branch Processor Registers
3.15.1.1 Machine State Register (MSR)
The floating-point exception mode encoding in the MPC555 / MPC556 core is as fol-
lows:
:
The SF bit is reserved set to zero
The IP bit initial state after reset is set as programmed by the reset configuration as
specified by the USIU specification.
3.15.1.2 Branch Processors Instructions
The MPC555 / MPC556 implements all the instructions defined for the branch proces-
sor in the
UISA
in the hardware.
3.15.2 Fixed-Point Processor
3.15.2.1 Special Purpose Registers
•
Unsupported Registers —
The following registers are not supported by the
MPC555 / MPC556: SDR, EAR, IBAT0U, IBAT0L, IBAT1U, IBAT1L, IBAT2U,
IBAT2L, IBAT3U, IBAT3L, DBAT0U, DBAT0L, DBAT1U, DBAT1L, DBAT2L,
Table 3-23 Floating-Point Exception Mode Encoding
Mode
FE0
FE1
Ignore exceptions
0
0
Precise
0
1
Precise
1
0
Precise
1
1
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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