Accessing Cp15 Registers; Terms And Abbreviations - Digi NS9750 Hardware Reference Manual

S y s t e m c o n t r o l p r o c e s s o r ( C P 1 5 ) r e g i s t e r s

Accessing CP15 registers

Use only
Figure 11 shows the MRC and MCR instruction bit pattern.
31
Cond
Figure 11: CP15 MRC and MCR bit pattern
The mnemonics for these instructions are:
MCR{cond} p15,opcode_1,Rd,CRn,CRm,opcode_2
MRC{cond} p15,opcode_1,Rd,CRn,CRm,opcode_2
If you try to read from a write-only register or write to a read-only register, you will
have
UNPREDICTABLE
The
to select the operations you want. Using other values results in
unpredictable behavior.
The
specified are used to select the behavior you want. Using other values
results in unpredictable behavior.

Terms and abbreviations

Table 17 lists the terms and abbreviations used in the CP15 registers and
explanations.
Term
UNPREDICTABLE
Table 17: CP15 terms and abbreviations
5 2
and instructions, only in privileged mode, to access CP15 registers.
MRC MCR
28 27 26 25 24 23 21 20 19
Opcode
1 1 1 0
_1
results. In all instructions that access CP15:
field
opcode_1 SHOULD BE ZERO
and fields
opcode_2 CRm
Abbreviation
UNP
N S 9 7 5 0 H a r d w a r e R e f e r e n c e
16 15 12 11 10
CRn Rd
L
, except when the values specified are used
, except when the values
SHOULD BE ZERO
Description
For reads:
The data returned when reading from this location is
unpredictable, and can have any value.
For writes:
Writing to this location causes unpredictable
behavior, or an unpredictable change in device
configuration.
9 8 7 5 4 3
Opcode
1 1 1 1 1
_2
0
CRm