| Unicore | |
| Designer: | Microprocessor Research and Development Center |
| Bits: | 32-bit |
| Introduced: | 1999 |
| Design: | RISC |
| Encoding: | Fixed |
| Branching: | Condition code |
| Endianness: | Little |
| Page Size: | 4 KiB |
| Gpr: | 31 |
| Fpr: | 32 |
Unicore is the name of a computer instruction set architecture designed by the Microprocessor Research and Development Center (MPRC) of Peking University in the PRC. The computer built on this architecture is called the Unity-863.[1] The CPU is integrated into a fully functional SoC to make a PC-like system.
The processor is very similar to the ARM architecture, but uses a different instruction set.[2]
It is supported by the Linux kernel as of version 2.6.39.[3] Support will be removed in Linux kernel version 5.9 as nobody seems to maintain it and the code is falling behind the rest of the kernel code and compiler requirements.[4]
The instructions are almost identical to the standard ARM formats, except that conditional execution has been removed, and the bits reassigned to expand all the register specifiers to 5 bits.[5] Likewise, the immediate format is 9 bits rotated by a 5-bit amount (rather than 8 bit rotated by 4), the load/store offset sizes are 14 bits for byte/word and 10 bits for signed byte or half-word. Conditional moves are provided by encoding the condition in the (unused by ARM) second source register field Rn for MOV and MVN instructions.
| Description | |||||||||||||||||||||||||||||||||
| 0 | 0 | 0 | opcode | S | Rn | Rd | shift | 0 | Sh | 0 | Rm | ALU operation, Rd = Rn op Rm shift #shift | |||||||||||||||||||||
| 0 | 0 | 0 | opcode | S | Rn | Rd | Rs | 0 | Sh | 1 | Rm | ALU operation, Rd = Rn op Rm shift Rs | |||||||||||||||||||||
| 0 | 0 | 1 | opcode | S | Rn | Rd | shift | imm9 | ALU operation, Rd = Rn op #imm9 ROTL #shift | ||||||||||||||||||||||||
| 0 | 1 | 0 | P | U | B | W | L | Rn | Rd | shift | 0 | Sh | 0 | Rm | Load/store Rd to address Rn ± Rm shift #shift | ||||||||||||||||||
| 0 | 1 | 1 | P | U | B | W | L | Rn | Rd | offset14 | Load/store Rd to address Rn ± offset14 | ||||||||||||||||||||||
| 1 | 0 | 0 | P | U | S | W | L | Rn | Bitmap high | 0 | 0 | H | Bitmap low | Load/store multiple registers | |||||||||||||||||||
| 1 | 0 | 1 | cond | L | offset24 | Branch (and link) if condition true | |||||||||||||||||||||||||||
| 1 | 1 | 0 | Coprocessor (FPU) instructions | ||||||||||||||||||||||||||||||
| 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | Trap number | Software interrupt | ||||||||||||||||||||||||
| 0 | 0 | 0 | 0 | 0 | 0 | A | S | Rn | Rd | Rs | 1 | 0 | 0 | 1 | Rm | Multiply, Rd = Rm * Rs (+ Rn) | |||||||||||||||||
| 0 | 0 | 0 | 1 | 0 | 0 | 0 | L | 11111 | 11111 | 00000 | 1 | 0 | 0 | 1 | Rm | Branch and exchange (BX, BLX) | |||||||||||||||||
| 0 | 1 | 0 | P | U | 0 | W | L | Rn | Rd | 00000 | 1 | S | H | 1 | Rm | Load/store Rd to address Rn ± Rm (16-bit) | |||||||||||||||||
| 0 | 1 | 0 | P | U | 1 | W | L | Rn | Rd | imm_hi | 1 | S | H | 1 | imm_lo | Load/store Rd to address Rn ± #imm10 (16-bit) | |||||||||||||||||
The meaning of various flag bits (such as S=1 enables setting the condition codes) is identical to the ARM instruction set. The load/store multiple instruction can only access half of the register set, depending on the H bit. If H=0, the 16 bits indicate R0–R15; if H=1, R16–R31.