L2 Description
4-18
The memory attribute registers (MARs) can be programmed to turn on caching
of each of the external chip enable (CE) spaces. In this way, you can perform
single word reads to external mapped devices. Without this feature any
external read would always read an entire L2 line of data. Each of the four CE
spaces is divided into four ranges, each of which maps the least significant bit
of an MAR register. If an MAR register is set, the corresponding address range
is cached by the L2. At reset, the MAR registers are set to 0. To begin caching
data in the L2, you must initialize the appropriate MAR register to 1. The MAR
registers define cacheability for the EMIF only. Addresses accessed by the
EMIF which are not defined by the MAR registers are always cacheable.
Figure 4–15 shows the format for the MARs. Table 4–3 illustrates which ad-
dress range each MAR bit enables for caching.
Figure 4–15. L2 CE Space Allocation Register Fields
MAR0
31
1
0
rsvd
CE 0.0
R,+x
RW,+0
MAR1
31
1
0
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CE 0.1
R,+x
RW,+0
MAR2
31
1
0
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CE 0.2
R,+x
RW,+0
MAR3
31
1
0
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CE 0.3
R,+x
RW,+0
MAR4
31
1
0
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CE 1.0
R,+x
RW,+0
MAR5
31
1
0
rsvd
CE 1.1
R,+x
RW,+0