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CHAPTER 2 V
R
4120A
Preliminary User’s Manual S14767EJ1V0UM00
131
2.4.6 Program compatibility
The V
R
4120A core is designed taking into consideration program compatibility with other V
R
-Series processors.
However, because the V
R
4120A differs from other processors in its architecture, it may not be able to run some
programs that run on other processors. Likewise, programs that run on the V
R
4120A will not necessarily run on other
processors. Matters which should be paid attention to when porting programs between the V
R
4120A core and other
V
R
-Series processors are listed below.
The V
R
4120A core does not support floating-point instructions since it has no Floating-Point Unit (FPU).
Multiply-add instructions (DMACC, MACC) are added in the V
R
4120A.
Instructions for power modes (HIBERNATE, STANDBY, SUSPEND) are added in the V
R
4120A to support
power modes.
The V
R
4120A does not have the LL bit to perform synchronization of multiprocessing. Therefore, the CPU
core does not support instructions which manipulate the LL bit (LL, LLD, SC, SCD).
A 16-bit length MIPS16 instruction set is added in the V
R
4120A.
The CP0 hazards of the V
R
4120A are equally or less stringent than those of other processors (for details, see
APPENDIX C V
R
4120A COPROCESSOR 0 HAZARDS
).
An instruction for debug has been added for the V
R
4120A. However, this instruction cannot be used for the
V
R
4120A.
For more information, refer to
Section 2.3 MIPS16 Instruction Set, APPENDIX A MIPS III INSTRUCTION SET
DETAILS
, the V
R
4100, V
R
4111 User's Manual, or the V
R
4300
User's Manual.
The list of instructions supported by V
R
-Series products is shown below.
Table 2-47. V
R
Series Supported Instructions
Product
Instruction
V
R
4100
V
R
4102
V
R
4111
V
R
4120A
Core
V
R
4300
V
R
4305
V
R
4310
V
R
5000
V
R
10000
MIPS I instruction set
Ο
Ο
Ο
Ο
Ο
MIPS II instruction set
Ο
Ο
Ο
Ο
Ο
MIPS III instruction set
Ο
Ο
Ο
Ο
Ο
LL bit operation
×
×
×
Ο
Ο
MIPS IV instruction set
×
×
×
×
Ο
MIPS16 instruction set
×
Ο
Ο
×
×
16-bit multiply-add operation
Ο
Ο
Ο
(Use of 32-bit
multiply-add
operation
×
×
32-bit multiply-add operation
×
×
Ο
×
×
Floating-point operation
×
×
×
Ο
Ο
Power mode transfer
Ο
Ο
Ο
×
×