ARM Technical Support Knowledge Articles

Why can MMU500 only configure SSDIndex 0-7?

Applies to: MMU-500 System Memory Management Unit

Answer

Each TBU only has up to 8 configurable SSD Indices.  You can specify an SSD Index Width that allows greater than 8 values but you must then choose up to 8 values within that range that can be configured.  Other indices within the range are fixed non-programmable, non-secure.

For example; if you configure TBU0's SSD Index Width to be 4 bits (giving an input of 0-15,) and then configure SSDIndex0 = 0x1 and SSDIndex1 = 0x7 as programmable secure in AMBA Designer the SSD indices for TBU0 will be:

0: non-programmable, non-secure
1: programmable, secure
2: non-programmable, non-secure
3: non-programmable, non-secure
4: non-programmable, non-secure
5: non-programmable, non-secure
6: non-programmable, non-secure
7: programmable, secure
8: non-programmable, non-secure
9: non-programmable, non-secure
10: non-programmable, non-secure
11: non-programmable, non-secure
12: non-programmable, non-secure
13: non-programmable, non-secure
14: non-programmable, non-secure
15: non-programmable, non-secure

Note that in the TCU programming interface the indices will be extended to 15 bits with the 5 most significant bits identifying the TBU.

Article last edited on: 2013-11-21 11:39:32

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