Chapter 1. Overview
1-37
Memory Management
1.8 Memory Management
The following subsections describe the memory management features of the PowerPC
architecture, and the MPC7400 implementation, respectively. A detailed description of the
MPC7400 MMU implementation is provided in Chapter 5, òMemory Management.ó
1.8.1 PowerPC Memory Management Model
The primary functions of the MMU are to translate logical (effective) addresses to physical
addresses for memory accesses and to provide access protection on blocks and pages of
memory. There are two types of accesses generated by the MPC7400 that require address
translationinstruction accesses, and data accesses to memory generated by load, store,
and cache control instructions.
System call
00C00
Execution of the System Call (
sc
) instruction.
Trace
00D00
MSR[SE] = 1 or a branch instruction completes and MSR[BE] = 1. Unlike the
architecture deTnition,
isync
does not cause a trace exception
Reserved
00E00
The MPC7400 does not generate an exception to this vector. Other
PowerPC processors may use this vector for oating-point assist exceptions.
Reserved
00E10D00EFF
Performance monitor
1
00F00
The limit speciTed in a PMC register is reached and MMCR0[ENINT] = 1
AltiVec unavailable
1
00F20
Occurs due to an attempt to execute any non-stream AltiVec instruction
while MSR[VA] = 0. This exception is not taken for stream instructions
(
dst
[
t
],
dstst
[
t
] or
dss
).
Instruction address
breakpoint
1
01300
IABR[0D29] matches EA[0D29] of the next instruction to complete, IABR[TE]
matches MSR[IR], and IABR[BE] = 1.
System management
interrupt
01400
MSR[EE] = 1 and SMI is asserted.
Reserved
01500D015FF
AltiVec assist
1
01600
Supports denormalization detection in Java mode as deTned by the AltiVec
speciTcation.
Thermal management
interrupt
1
01700
Thermal management is enabled, the junction temperature exceeds the
threshold speciTed in THRM1 or THRM2, and MSR[EE] = 1.
Reserved
01800D02FFF
1
MPC7400-speciTc
Table 1-6. Exceptions and Conditions (Continued)
Exception Type
Vector Offset
(hex)
Causing Conditions