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CHAPTER 3 CP0 REGISTERS
User’s Manual U14272EJ3V0UM
83
3.2.15 Config register (16)
The Config register specifies various configuration options selected on the V
R
4181.
Some configuration options, as defined by the EC and BE fields, are set by the hardware during Cold Reset and
are included in the Config register as read-only status bits for the software to access. Other configuration options
(AD, EP, and K0 fields) can be read/written and controlled by software; on Cold Reset these fields are undefined.
Since only a subset of the V
R
4000 Series
bits 14 and 13) that were variable in the V
R
4000 Series. The Config register should be initialized by software before
caches are used.
The contents of the Config register are undefined after a reset so that it must be initialized by software.
TM
options are available in the V
R
4181, some bits are set to constants (e.g.,
Caution
Be sure to set the EP field and the AD bit to 0. If they are set with any other values, the
processor may behave unexpectedly.
Figure 3-18. Config Register (1/2)
31 30
28 27
24 23 22 21 2019 18 17 16 15 14 13 12 11
9 8
6 5
3 2
0
0
EC
EP
AD
0
M16
0
1
0 BE
10
CS
IC
DC
0
K0
EC:
System clock ratio (read only)
0
→
Processor clock frequency divided by 2
1
→
Processor clock frequency divided by 3
2
→
Processor clock frequency divided by 4
3 to 7
→
Reserved
Transfer data pattern (cache write-back pattern) setting
0
→
DD: 1 word per 1 cycle
Others
→
Reserved
Accelerate data mode
0
→
V
R
4000 Series compatible mode
1
→
Reserved
MIPS16 ISA mode enable/disable indication (read only)
0
→
MIPS16 instruction cannot be executed
1
→
MIPS16 instruction can be executed.
BigEndianMem (Endian mode indication)
0
→
Little endian
1
→
Reserved
Cache size mode indication (n = IC, DC)
0
→
Reserved
1
→
2
Instruction cache size indication. 2
2
→
4 KB
Others
→
Reserved
Data cache size indication. 2
2
→
4 KB
Others
→
Reserved
EP:
AD:
M16:
BE:
CS:
(n+10)
bytes
IC:
(IC+10)
bytes in the V
R
4181.
DC:
(DC+10)
bytes in the V
R
4181.