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Functional Description
2-8
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ARM DDI 0414C
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Table 2-5 shows the
MBISTBE
bits used to control the tag RAMs.
Outer RAM
Outer RAM consists of one array per CPU. It is a bit-writable RAM. Bit-write enables
must be controllable separately.
MBISTARRAY[17]
selects the Outer RAM array.
Figure 2-7 and Figure 2-8 show the data mapping on
MBISTINDATA
and
MBISTOUTDATA
buses for Outer RAM.
Figure 2-7 Data in for Outer RAM
Figure 2-8 Data out for Outer RAM
Branch Target Address Cache RAM
Branch Target Address Cache
(BTAC) RAMs consist of two arrays, one for control and
one for target. The target array is always 32 bits wide.
MBISTARRAY[1:0]
selects the BTAC array. They are word-writable, controlled by
MBISTWRITEEN
when in BIST mode.
Table 2-5 Tag RAM control
RAM type
Write enable
MBISTBE bits
SCU tag RAM
Bit-write enable
[22:0]
Data tag RAM
Bit-write enable
[25:0]
MBISTINDATA[63:0]
Outer Data in [11:0]
Unused
31
32
0
63
27
28
MBISTOUTDATA[255:0]
63
0
127
128
191
192
255
64
Unused
Data out
[11:0]
Data out [63:0] for CPU3
Data out [63:0] for CPU2
Data out [63:0] for CPU1
Data out [63:0] for CPU0
Unused
Data out
[11:0]
Unused
Data out
[11:0]
Unused
Data out
[11:0]