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4.3.1. General-Purpose Register File
4.3.2. Arithmetic Logic Unit
4.3.3. Multipy and Divide Units
4.3.4. Floating-Point Unit
4.3.5. Custom Instruction
4.3.6. Reset and Debug Signals
4.3.7. Control and Status Registers
4.3.8. Exception Controller
4.3.9. Interrupt Controller
4.3.10. Memory and I/O Organization
4.3.11. RISC-V based Debug Module
4.3.12. Error Correction Code (ECC)
4.3.10.4. Tightly Coupled Memory
Tightly coupled memory (TCM) guarantees fixed low-latency memory access for performance-critical applications. The advantages of TCM over cache memory are as follows:
- Performance similar to cache memory
- Software can guarantee that performance-critical code or data is located in TCM
- No real-time caching overhead, such as loading, invalidating, or flushing memory
Physically, a TCM is a dedicated on-chip memory within the Nios® V processor core. Intel implements TCM using the M20K memory blocks. The Nios® V processor architecture supports four TCMs for instruction access and data access (two per access type). Each TCM provide an AXI4-Lite interface for connection with an external master, or manager. The interconnect would allow you to connect Avalon® or other supported manager, gaining access to read or write the respective TCMs.