Semiconductor & Computer Engineering
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μCOM-4 ISA - NEC
The μCOM-4 ISA was an instruction set architecture composed of 80 instructions that were implemented by the NEC in their μCOM-4 family of microcontrollers. The μCOM-43 family implemented the complete ISA, while the μCOM-44 and μCOM-45 families implemented a strict subset of it. (Note that the μCOM-42 family had its own instruction set.)
Block diagram
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Registers
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Features
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Instructions
The μCOM-43 has support for all 80 instructions. The μCOM-44/μCOM-45 support a strict subset of it composed of 58 instruction. The majority of those 22 instructions deal with the added features only found in the μCOM-43 models.
| Mnemonic | OPCode | Bytes | Cycles | Meaning | Skip Condition |
|---|---|---|---|---|---|
| CLA | 1 | 1 | ACC ← 0 | ||
| CMA | 1 | ||||
| CIA | 1 | ||||
| INC | 1 | ||||
| DEC | 1 | ||||
| CLC | 1 | ||||
| STC | 1 | ||||
| XC | 1 | ||||
| RAR | 1 | ||||
| INM | 1 | ||||
| DEM | 1 | ||||
| AD | 1 | ||||
| ADS | 1 | ||||
| ADC | 1 | ||||
| DAA | 1 | ||||
| DAS | 1 | ||||
| EXL | 1 | ||||
| LI | 1 | ||||
| S | 1 | ||||
| L | 1 | ||||
| LM | 1 | ||||
| X | 1 | ||||
| XM | 1 | ||||
| XD | 1 | ||||
| XMD | 1 | ||||
| XI | 1 | ||||
| XMI | 1 | ||||
| LDI | 2 | ||||
| LDZ | 1 | ||||
| DED | 1 | ||||
| IND | 1 | ||||
| TAL | 1 | ||||
| TLA | 1 | ||||
| XHX | 1 | ||||
| XLY | 1 | ||||
| THX | 1 | ||||
| TLY | 1 | ||||
| XAZ | 1 | ||||
| XAW | 1 | ||||
| TAZ | 1 | ||||
| TAW | 1 | ||||
| XHR | 1 | ||||
| XLS | 1 | ||||
| SMB | 1 | ||||
| RMB | 1 | ||||
| TMB | 1 | ||||
| TAB | 1 | ||||
| CMB | 1 | ||||
| SFB | 1 | ||||
| RFB | 1 | ||||
| FBT | 1 | ||||
| FBF | 1 | ||||
| CM | 1 | ||||
| CI | 2 | ||||
| CLI | 2 | ||||
| TC | 1 | ||||
| TIT | 1 | ||||
| JCP | 1 | ||||
| JMP | 2 | ||||
| JPA | 1 | ||||
| EI | 1 | ||||
| DI | 1 | ||||
| CZP | 1 | ||||
| CAL | 2 | ||||
| RT | 1 | ||||
| RTS | 1 | ||||
| STM | 2 | ||||
| TTM | 1 | ||||
| SEB | 1 | ||||
| REB | 1 | ||||
| SPB | 1 | ||||
| RPB | 1 | ||||
| TPA | 1 | ||||
| TPB | 1 | ||||
| OE | 1 | ||||
| OP | 1 | ||||
| OCD | 2 | 2 | PORT[C,D] ← I7-I0 | ||
| IA | 2 | 2 | ACC ← PORT[A] | ||
| IP | 1 | 1 | ACC ← PORT[DPL] | ||
| NOP | 1 | 1 | no operation |
- μCOM-43 only
