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CHAPTER 2 V
R
4120A
Preliminary User’s Manual S14767EJ1V0UM00
63
Table 2-1. System Control Coprocessor (CP0) Register Definitions
Register Number
Register Name
Description
0
Index
Programmable pointer to TLB array
1
Random
Pseudo-random pointer to TLB array (read only)
2
EntryLo0
Low half of TLB entry for even VPN
3
EntryLo1
Low half of TLB entry for odd VPN
4
Context
Pointer to kernel virtual PTE in 32-bit mode
5
PageMask
TLB page mask
6
Wired
Number of wired TLB entries
7
Reserved for future use
8
BadVAddr
Virtual address where the most recent error occurred
9
Count
Timer count
10
EntryHi
High half of TLB entry (including ASID)
11
Compare
Timer compare
12
Status
Status register
13
Cause
Cause of last exception
14
EPC
Exception Program Counter
15
PRId
Processor revision identifier
16
Config
Configuration register (specifying memory mode system)
17
LLAddr
Reserved for future use
18
WatchLo
Memory reference trap address low bits
19
WatchHi
Memory reference trap address high bits
20
XContext
Pointer to kernel virtual PTE in 64-bit mode
21 to 25
Reserved for future use
26
PErr
Note
Cache parity bits
27
CacheErr
Note
Index and status of cache error
28
TagLo
Cache Tag register (low)
29
TagHi
Cache Tag register (high)
30
ErrorEPC
Error Exception Program Counter
31
Reserved for future use
Note
This register is defined to maintain compatibility with the V
R
4100. This register is not used in
the
μ
PD98501 hardware.
2.1.6 Floating-point unit (FPU)
The V
R
4120A does not support the floating-point unit (FPU). Coprocessor Unusable exception will occur if any
FPU instructions are executed. If necessary, FPU instructions should be emulated by software in an exception
handler.