2. RV32I basic instruction set
The basic instruction set, called RV32I, comprises 47 instructions. There are 32 32-bit registers named x0 to x31 and a program counter (pc). Register x0 contains 0 and can be used as the destination register of an instruction when the result is not used.
2.1 Instruction format
Instructions are of fixed 32-bit size, with a 7-bit opcode, i.e. 128 fundamental opcodes (table 1 ). For RV32I, the two bits [1:0] of the opcode are 11, which means that the remaining 75% of opcodes are available for the various extensions presented in Chapters 3, 4 and 5. On the other hand, only 11 of the 32 opcodes are actually used, i.e. 8.6% of the total number of fundamental opcodes.
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RV32I basic instruction set
Basic extensions
Bibliography
- (1) - HILL (M.D.), CHRISTIE (D.), PATERSON (D.), YI (J.J.), CHIOU (D.), SENDAG (R.) - Proprietary versus Open Instruction Sets, - IEEE Micro, pp 58-68, July-August 2016. https://research.cs.wisc.edu/multifacet/papers/ieeemicro16_card_isa.pdf ...
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