
W O R K I N G W I T H T H E C P U
R1: Control register
90
Hardware Reference NS9215
ICache and
DCache behavior
The M, C, I, and RR bits directly affect ICache and DCache behavior, as shown:
If either the DCache or ICache is disabled, the contents of that cache are not
accessed. If the cache subsequently is re-enabled, the contents will not have
changed. To guarantee that memory coherency is maintained, the DCache must be
cleaned of dirty data before it is disabled.
[6:3]
N/A
Reserved.
SHOULD BE ONE.
[2]
C bit
DCache enable/disable
0
Cache disabled
1
Cache enabled
[1]
A bit
Alignment fault enable/disable
0
Data address alignment fault checking disabled
1
Data address alignment fault checking enabled
[0]
M bit
MMU enable/disable
0
Disabled
1
Enabled
Bits
Name
Function
Cache
MMU
Behavior
ICache disabled
Enabled or disabled
All instruction fetches are from external memory (AHB).
ICache enabled
Disabled
All instruction fetches are cachable, with no protection
checking. All addresses are flat-mapped; that is:
VA=MVA=PA.
ICache enabled
Enabled
Instruction fetches are cachable or noncachable, and
protection checks are performed. All addresses are
remapped from VA to PA, depending on the MMU page
table entry; that is, VA translated to MVA, MVA
remapped to PA.
DCache disabled
Enabled or disabled
All data accesses are to external memory (AHB).
DCache enabled
Disabled
All data accesses are noncachable nonbufferable. All
addresses are flat-mapped; that is, VA=MVA=PA.
DCache enabled
Enabled
All data accesses are cachable or noncachable, and
protection checks are performed. All addresses are
remapped from VA to PA, depending on the MMU page
table entry; that is, VA translated to MVA, MVA
remapped to PA.
Summary of Contents for NS9215
Page 1: ...NS9215 Hardware Reference 90000847_C Release date 10 April 2008...
Page 3: ......
Page 4: ......
Page 26: ...26 Hardware Reference NS9215...
Page 44: ...P I N O U T 26 5 System clock 44 Hardware Reference NS9215 System clock drawing...
Page 52: ...P I N O U T 26 5 Power and ground 52 Hardware Reference NS9215...
Page 80: ...I O C O N T ROL M O D U L E Memory Bus Configuration register 80 Hardware Reference NS9215...
Page 136: ...WOR KI N G W I TH T H E C P U Noncachable instruction fetches 136 Hardware Reference NS9215...
Page 202: ...S Y S T E M C O N T RO L M OD U L E RTC Module Control register 202 Hardware Reference NS9215...
Page 354: ...E X T E R N A L D M A DMA Peripheral Chip Select register 354 Hardware Reference NS9215...
Page 472: ...R E A L TI M E C L O C K M O D U L E General Status register 472 Hardware Reference NS9215...
Page 512: ...TI M I NG Clock timing 512 Hardware Reference NS9215...
Page 515: ...PA CKA GING Processor Dimensions www digiembedded com 515...
Page 516: ...PA CKA GING Processor Dimensions 516 Hardware Reference NS9215...