u-boot/doc/README.NX25
Rick Chen 3fafced74d riscv: doc: Add relative doc to describe RISC-V
Add documents to describe NX25 and AE250.
Also update other documents for RISC-V.

Signed-off-by: Rick Chen <rick@andestech.com>
Signed-off-by: Rick Chen <rickchen36@gmail.com>
Signed-off-by: Greentime Hu <green.hu@gmail.com>
2018-01-12 08:05:12 -05:00

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NX25 is Andes CPU IP to adopt RISC-V architecture.
Features
========
CPU Core
- 5-stage in-order execution pipeline
- Hardware Multiplier
- radix-2/radix-4/radix-16/radix-256/fast
- Hardware Divider
- Optional branch prediction
- Machine mode and optional user mode
- Optional performance monitoring
ISA
- RV64I base integer instructions
- RVC for 16-bit compressed instructions
- RVM for multiplication and division instructions
Memory subsystem
- I & D local memory
- Size: 4KB to 16MB
- Memory subsyetem soft-error protection
- Protection scheme: parity-checking or error-checking-and-correction (ECC)
- Automatic hardware error correction
Bus
- Interface Protocol
- Synchronous AHB (32-bit/64-bit data-width), or
- Synchronous AXI4 (64-bit data-width)
Power management
- Wait for interrupt (WFI) mode
Debug
- Configurable number of breakpoints: 2/4/8
- External Debug Module
- AHB slave port
- External JTAG debug transport module
Platform Level Interrupt Controller (PLIC)
- AHB slave port
- Configurable number of interrupts: 1-1023
- Configurable number of interrupt priorities: 3/7/15/63/127/255
- Configurable number of targets: 1-16
- Preempted interrupt priority stack