
2-12
G2 PowerPC Core Reference Manual
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MOTOROLA
Register Set
11
DPM
1
Dynamic power management enable
0 Dynamic power management is disabled
1 Functional units enter a low-power mode automatically if the unit is idle. This does not affect
operational performance and is transparent to software or any external hardware.
12–15
—
Reserved, should be cleared.
16
ICE
2
Instruction cache enable
0 The instruction cache is neither accessed nor updated. All pages are accessed as if they were
marked cache-inhibited (WIM = x1x). Potential cache accesses from the bus (snoop and cache
operations) are ignored. In the disabled state for the L1 caches, the cache tag state bits are
ignored and all accesses are propagated to the 60x bus as single-beat transactions. For those
transactions, however, core_ci reflects the state of the I bit in the MMU for that page regardless
of cache disabled status. ICE is zero at power-up.
1 The instruction cache is enabled
17
DCE
Data cache enable
0 The data cache is neither accessed nor updated. All pages are accessed as if they were
marked cache-inhibited (WIM = x1x). Potential cache accesses from the 60x bus (snoop and
cache operations) are ignored. In the disabled state for the L1 caches, the cache tag state bits
are ignored and all accesses are propagated to the 60x bus as single-beat transactions. For
those transactions, however, core_ci reflects the state of the I bit in the MMU for that page
regardless of cache disabled status. DCE is zero at power-up.
1 The data cache is enabled
18
ILOCK
Instruction cache lock
0 Normal operation
1 Instruction cache is locked. A locked cache supplies data normally on a hit, but the access is
treated as a cache-inhibited transaction on a miss. On a miss, the transaction to the 60x bus is
single-beat; however, core_ci still reflects the state of the I bit in the MMU for that page
independent of cache locked or disabled status.
To prevent locking during a cache access, an
isync
instruction must precede the setting of ILOCK.
19
DLOCK
Data cache lock
0 Normal operation
1 Data cache is locked. A locked cache supplies data normally on a hit, but is treated as a
cache-inhibited transaction on a miss. On a miss, the transaction to the 60x bus is single-beat;
however, core_ci still reflects the state of the I bit in the MMU for that page independent of cache
locked or disabled status. A snoop hit to a locked L1 data cache performs as if the cache were
not locked. A cache block invalidated by a snoop remains invalid until the cache is unlocked.
To prevent locking during a cache access, a
sync
instruction must precede the setting of DLOCK.
20
ICFI
Instruction cache flash invalidate
0 The instruction cache is not invalidated. The bit is cleared when the invalidation operation
begins (usually the next cycle after the write operation to the register). The instruction cache
must be enabled for the invalidation to occur.
1 An invalidate operation is issued that marks the state of each instruction cache block as invalid
without writing back modified cache blocks to memory. Cache access is blocked during this
time. Bus accesses to the cache are signaled as a miss during invalidate-all operations. Setting
ICFI clears all the valid bits of the blocks and the PLRU bits to point to way L0 of each set.
For the G2 core, the proper use of the ICFI and DCFI bits is to set and clear them with two
consecutive
mtspr
operations.
Table 2-5. HID0 Bit Functions (continued)
Bits
Name
Function
F
Freescale Semiconductor, Inc.
n
.