10-10
MPC7400 RISC Microprocessor Users Manual
Thermal Assist Unit (TAU)
temperature sampling is suspended, and the THRM
n
[TIN] and THRM
n
[TIV] values are
held until an
mtspr
instruction is executed to THRM
n
.
The execution of an
mtspr
instruction to THRM
n
anytime during thermal assist unit
operation clears THRM
n
[TIV] and restarts the temperature comparison. Executing an
mtspr
instruction to THRM3 clears THRM1[TIV] and THRM2[TIV] and restarts
temperature comparison in THRM
n
if THRM3[E] = 1.
Examples of valid THRM1 and THRM2 bit settings are shown in Table 10-4.
10.3.2.2 Thermal Assist Unit Dual-Threshold Mode
The conTguration and operation of dual-threshold mode is similar to single-threshold
mode, except both THRM1 and THRM2 are conTgured with desired threshold and TID
values, and the TIE and V bits are set. When THRM3[E] is set, enabling temperature
measurement and comparison, the Trst comparison is made with THRM1. If no thermal
management interrupt results from the comparison, the number of processor cycles
speciTed in THRM3[SITV] elapses, and the next comparison is made with THRM2. If no
thermal management interrupt results from the THRM2 comparison, the time speciTed by
THRM3[SITV] again elapses, and the comparison returns to THRM1.
This sequence of comparisons continues until a thermal management interrupt occurs, or
the thermal assist unit is disabled. When a comparison results in an interrupt, the
Table 10-4. Valid THRM1 and THRM2 Bit Settings
TIN
1
1
The TIN and TIV bits are read-only status bits.
TIV
1
TID
TIE
V
Description
x
x
x
x
0
The threshold in the SPR is not used for comparison.
x
x
x
0
1
Threshold is used for comparison, thermal management interrupt assertion is disabled.
x
x
0
0
1
Set TIN and do not assert thermal management interrupt if the junction temperature
exceeds the threshold.
x
x
0
1
1
Set TIN and assert thermal management interrupt if the junction temperature exceeds
the threshold.
x
x
1
0
1
Set TIN and do not assert thermal management interrupt if the junction temperature is
less than the threshold.
x
x
1
1
1
Set TIN and assert thermal management interrupt if the junction temperature is less
than the threshold.
x
0
x
x
1
The state of the TIN bit is not valid.
0
1
0
x
1
The junction temperature is less than the threshold and as a result the thermal
management interrupt is not generated for TIE = 1.
1
1
0
x
1
The junction temperature is greater than the threshold and as a result the thermal
management interrupt is generated if TIE = 1.
0
1
1
x
1
The junction temperature is greater than the threshold and as a result the thermal
management interrupt is not generated for TIE = 1.
1
1
1
x
1
The junction temperature is less than the threshold and as a result the thermal
management interrupt is generated if TIE = 1.