Memory Controller
MOTOROLA
MPC823e REFERENCE MANUAL
15-41
MEMORY CONTROLLER
15
MEMORY CONTROLLER
15
15.5.1 Requests
The user-programmable machine has four basic requests that can initiate a UPM cycle.
There is a special start address in the RAM array that is associated with each of the following
cycle types:
• Read single beat start address (RSS)
• Read burst cycle start address (RBS)
• Write single beat start address (WSS)
• Write burst cycle start address (WBS)
• Periodic timer start address (PTS)
• Exception condition start address (EXS)
Figure 15-21 illustrates the first locations addressed by the UPM, according to the different
cycle types. Software requests, however, can point to any of the 64 UPM RAM entries.
Figure 15-21. RAM Array Indexing
64
RSS
WSS
RBS
WBS
PTS
BURST READ REQUEST
BURST WRITE REQUEST
READ SINGLE BEAT REQUEST
WRITE SINGLE BEAT REQUEST
PERIODIC TIMER REQUEST
EXS
EXCEPTION CONDITION
RAM ARRAY
ARRAY
INDEX
GENERATOR
RAM
WORDS
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