2-10
MPC7400 RISC Microprocessor Users Manual
The MPC7400 Processor Register Set
D THRM1 and THRM2 provide the ability to compare the junction temperature
against two user-provided thresholds. The dual thresholds allow the thermal
management software differing degrees of action in lowering the junction
temperature. The TAU can be also operated in a single threshold mode in
which the thermal sensor output is compared to only one threshold in either
THRM1 or THRM2.
D THRM3 is used to enable the thermal management assist unit (TAU) and to
control the comparator output sample time.
D The processor identiTcation register (PIR) is provided for use by the system.
MPC7400 does not do anything to the contents of this register.
Note that while it is not guaranteed that the implementation of MPC7400-speciTc registers
is consistent among PowerPC processors, other processors can implement similar or
identical registers.
2.1.2 MPC7400-SpeciTc Registers
This section describes registers that are deTned for the MPC7400 but are not included in
the PowerPC architecture. All the registers described in
The AltiVec Technology
Programming Environments Manual
are implemented in MPC7400. See Chapter 2,
òAltiVec Register Set,ó in
The AltiVec Technology Programming Environments Manual
for
details about these registers.
2.1.2.1 Instruction Address Breakpoint Register (IABR)
The instruction address breakpoint register (IABR), shown in Table 2-2, supports the
instruction address breakpoint exception. When this exception is enabled, instruction fetch
addresses are compared with an effective address stored in the IABR. If the word speciTed
in the IABR is fetched, the instruction breakpoint handler is invoked. The instruction that
triggers the breakpoint does not execute before the handler is invoked. For more
information, see Section 4.6.14, òInstruction Address Breakpoint Exception (0x01300).ó
The IABR can be accessed with
mtspr
and
mfspr
using the SPR 1010. The MPC7400
requires that an
mtspr
(IABR) be followed by a context synchronizing instruction.
Figure 2-2. Instruction Address Breakpoint Register
0
29 30 31
Address
BE TE