Subversion Repositories neorv32

## Project Change Log

The most recent **NEORV32** project version can be found on top of this list.
"Officially released" versions are linked and highlighted (:rocket:).
The latest release is [![release](https://img.shields.io/github/v/release/stnolting/neorv32)](https://github.com/stnolting/neorv32/releases).
A list of all releases can be found [here](https://github.com/stnolting/neorv32/releases). The most recent version of the *NEORV32 data sheet*
can be found [here](https://raw.githubusercontent.com/stnolting/neorv32/master/docs/NEORV32.pdf) (pdf).

The processor can determine its version from the `mimpid` CSR (at CSR address 0xf13). A 2x4-bit decimal-coded representation is used. Leading
zeros are optional. Example: `CSR(mimpid) = 0x01040312 -> 01.04.03.12 -> Version 1.4.3.12 = v1.4.3.12 = v01.04.03.12`

For the HDL sources the version number is globally defined by the `hw_version_c` constant in the main VHDL package file
[`rtl/core/neorv32_package.vhd`](https://github.com/stnolting/neorv32/blob/master/rtl/core/neorv32_package.vhd).

| Date (*dd.mm.yyyy*) | Version | Comment |
|:----------:|:-------:|:--------|
| 24.10.2020 | [**:rocket:1.4.6.0**](https://github.com/stnolting/neorv32/releases/tag/v1.4.6.0) | Completely reworked external memory interface (WISHBONE), removed now-obsolete processor generic `MEM_EXT_REG_STAGES`; added processor wrapper with **AXI4-Lite master interface** |
| 22.10.2020 | 1.4.5.11 | TWI: Added new control register flag to enable/disable SCL clock stretching by peripheral devices |
| 22.10.2020 | 1.4.5.10 | Added `i_bus_priv_o` and `d_bus_priv_o` signals to CPU_top and `priv_o` to Processor_top to show privilege level of bus access (from `mstatus` MPP); :warning: Fixed bug in external memory interface [WISHBONE] (non-standard Wishbone components were able to corrupt processor-internal ACK/ERR signal logic) |
| 20.10.2020 | 1.4.5.9 | :warning: Fixed bug in CPU "sleep" instruction (`WFI` - wait for interrupt) |
| 20.10.2020 | 1.4.5.8 | *Machine timer interrupt* is available as processor input pin (`mtime_irq_i`) if internal `MTIME` is not implemented (`IO_MTIME_USE` = false) |
| 18.10.2020 | 1.4.5.7 | Added new IO peripheral/Device: Second CFU (CFU1); renamed old CFU to CFU0; CFU VHDL files: `neorv32_cfu0.vhd` & `neorv32_cfu1.vhd`; removed CFU interrupt |
| 17.10.2020 | 1.4.5.5 | New makefile target `upload` allows to directly upload an executable to the bootloader from the console |
| 17.10.2020 | 1.4.5.4 | Added new CPU/Processor generic `FAST_SHIFT_EN` (default = *false*) to enable implementation of a fast (but large) barrel shifter for accelerating CPU shift instructions; updated CoreMark performance results |
| 16.10.2020 | 1.4.5.2 | Added read-only flag to custom `mzext` CSR to check if physical memory protection (PMP) is implemented; added [C] `mzext` CSR name aliases to neorv32.h |
| 15.10.2020 | 1.4.5.1 | Fixed "unprecise exceptions": `mtval` did not always reflect the correct value according to the instruction that caused the exceptions; fixed bug in RTE: Debug trap handler was not showing the correct `mepc` value |
| 13.10.2020 | [**:rocket:1.4.5.0**](https://github.com/stnolting/neorv32/releases/tag/v1.4.5.0) | An official *open-soucre RISC-V architecture ID* was assigned to the project: decimal = `19`, 32-bit hexadecimal = `0x00000013` - software can retrieve the ID from the `marchid` CSR |
| 12.10.2020 | 1.4.4.9 | Added *alignment flags* to makefiles: branch/jump/call targets are forced to be 32-bit aligned -> increases performance when using the `C` extension; added makefile flag listing to NEORV32.pdf; updated performance results for CPUs with `C` extension; `crt0.S` will initialize *all* registers with zero if not using `E` extension and not compiling bootloader |
| 11.10.2020 | 1.4.4.8 | Reworked pipeline frontend: Optimized fetch enginge, added issue engine, faster instruction fetch after taken branches + reduced hardware requirements; updated synthesis and performance results |
| 11.10.2020 | 1.4.4.6 | Added option to configure external memory interface (Wishbone) to either use *standard/classic protocol* (default) or *pipelined protocol* (for better timing): via `wb_pipe_mode_c` constant in VHDL package file (`rtl/core/neorv32_package.vhd`); added help text to NEORV32.pdf section "3.4.4. Processor-External Memory Interface (WISHBONE)" |
| 08.10.2020 | 1.4.4.5 | Removed CPU's `BUS_TIMEOUT` and processor's `MEM_EXT_TIMEOUT` generics; instead, a global configuration `bus_timeout_c` in the VHDL package file is used now |
| 08.10.2020 | 1.4.4.4 | Removed `DEVNULL` device; all simulation output options from this device are now available as `SIM_MODE` in the `UART`; `mcause` CSR can now also be written; FIXED: trying to write a read-only CSR will cause an illegal instruction exception; for compatibility reasons any write access to the misa CSR will be ignored and will NOT cause an exception |
| 07.10.2020 | 1.4.4.2 | Simplified ALU's set of core operations; removed co-processor data mux right after ALU -> shorter critical path; CPU control VHDL code clean-up and CSR write logic optimization; optimized IMEM/DMEM access logic; added note regarding alignment of IMEM/DMEM |
| 05.10.2020 | [**:rocket:1.4.4.0**](https://github.com/stnolting/neorv32/releases/tag/v1.4.4.0) | :warning: Fixed bug in external memory interface: Executing code from external memory was causing an instruction fetch stall |
| 02.10.2020 | 1.4.3.9 | `[m]cycleh` and `[m]instreth` CSRs are now 32-bit wide (-> fully RISC-V-compliant) |
| 01.10.2020 | 1.4.3.8 | Added CPU top entity wrapper with resolved port signals `rtl/top_templetes/neorv32_cpu_stdlogic.vhd`; optimized ALU core functions – shorter critical path, less control overhead, reduced HW footprint |
| 27.09.2020 | 1.4.3.3 | Further improved ALU and control logic; CSR access instruction require one additional cycle now (to let side effects kick in); updated synthesis results; added CFU hardware driver dummy |
| 26.09.2020 | 1.4.3.2 | :warning: Fixed bug in `CSRRWI` instruction (introduced with version 1.4.3.1); further ALU operand logic optimizations; updated CPU data path figure |
| 25.09.2020 | 1.4.3.1 | Register file's `x0` is now a physical register; this register is initialized by the hardware and locked afterwards; removed "set to zero" stage -> smaller hardware footprint and shorter critical path; added processor top entity wrapper with resolved signals `rtl/top_templetes/neorv32_top_stdlogic.vhd` |
| 16.09.2020 | [**:rocket:1.4.3.0**](https://github.com/stnolting/neorv32/releases/tag/v1.4.3.0) | Simplified memory configuration: removed processor top's memory space configuration generics (`MEM_ISPACE_BASE`, `MEM_ISPACE_SIZE`, `MEM_DSPACE_BASE`, `MEM_DSPACE_SIZE`); data/instruction space sizes are irrelevant for hardware; instruction/data space base addresses are fixed (but can be modified in NEORV32 VHDL package file); modified SYSINFO registers; adapted bootloader, crt0 start-up code and linker script; stack configuration is now done via linker script; reworked chapter "address space"; added CFU interrupt -> fast interrupt channel 1 (shared with GPIO) |
| 14.09.2020 | 1.4.2.0 | Removed option to disable CSR counters (via `CSR_COUNTERS_USE` generic) since these counters are mandatory according to the RISC-V specs; added new IO/peripheral device: custom functions unit (`CFU`) for tightly-coupled custom co-processors; improved timing of processor-internal clock generator; fixed wrong labels in address space figure and removed dedicated exception vectors box; added mask register to GPIO unit to specify which input pins can trigger a pin-change interrupt |
| 11.09.2020 | 1.4.0.4 | Reworked `TRNG` architecture and interface; added text regarding fast interrupt channels usage for the NEORV32 processor |
| 02.09.2020 | 1.4.0.2 | :warning: Fixed bugs in external memory interface; added option to define latency of simulated external memory in testbench; hardware configuration sanity checks will now only appear once in console; added more details to data sheet section 3.3. Address Space; fixed typos in MEM_*_BASE and MEM_*_SIZE generic names |
| 01.09.2020 | 1.4.0.1 | Using registers above `x15` when the `E` extensions is enabled will now correctly cause an illegal instruction exception |
| 29.08.2020 | [**:rocket:1.4.0.0**](https://github.com/stnolting/neorv32/releases/tag/v1.4.0.0) | Rearranged and reworked this document; added FreeRTOS port, demo & short referencing chapter; removed booloader-specific linker scripts – main linker script is used for both, applications and bootloader; bootloader can now have `.data` and `.bss` sections; improved IMEM and BOOTROM memory initialization – faster synthesis; image generator now constrains init array size to actual executable size; peripheral/IO devices can only be written in full word mode (= 32-bit); GPIO ports are now 32-bit wide |
| 23.08.2020 | 1.3.7.3 | Added custom `mzext` CSR to check for available Z* CPU extensions; multiplier's FAST_MUL mode is one cycle faster now; updated performance data |
| 20.08.2020 | 1.3.7.2 | Removed bootloader-specific crt0 – bootloader now uses std crt0; makefiles now also support asm and cpp files; made linker scripts more general; renamed makefile "compile" (which is still available for compatibility) target into "exe" |
| 14.08.2020 | [**:rocket:1.3.7.0**](https://github.com/stnolting/neorv32/releases/tag/v1.3.7.0) | Simplified CPU fetch engine; added configurable CPU instruction prefetch buffer (ipb) FIFO; optimized CPU execute engine; updated performance data |
| 06.08.2020 | 1.3.6.5 | Added `FAST_MUL_EN` generic to enable mapping of the multiplier core to DSP blocks; ALU.shifter is no more triggered when executing MULDIV operations; added benchmark results for DSP-based multiplier configurations; updated implementation and performance results; simplified makefiles – using implicit libc definition; crt0 only initializes lowest 16 registers |
| 03.08.2020 | [**:rocket:1.3.6.0**](https://github.com/stnolting/neorv32/releases/tag/v1.3.6.0) | Relocated `DEVNULL` (changed base address); minor edits, optimization and clean-ups |
| 30.07.2020 | 1.3.5.2 | Added register stage to PMP mask generation to shorten critical path; removed automatic IRQ enable/disable from RTE install/uninstall functions |
| 30.07.2020 | 1.3.5.1 | :warning: Fixed bug(s) in PMP mask generation; `misa.Z` flag is not yet defined by the RISC-V specs., hence it is read-only and read as zero |
| 29.07.2020 | 1.3.5.0 | Added user privilege level, enabled via new `CPU_EXTENSION_RISCV_U` generic; :warning: fixed error in `mstatus(mpie)` logic; implemented RISC-V spec.-compliant Physical Memory Protection (PMP); allows up to 8 regions but only NAPOT mode is supported yet |
| 25.07.2020 | 1.3.0.0 | `mcause` CSR is read-only now!; removed `CLIC`, added 4 fast IRQ channels to CPU with according flags in `mie` and `mip` and trap IDs; updated core libraries; updated NEORV32 RTE; highly reworked data sheet; updated synthesis and performance results |
| 21.07.2020 | 1.2.0.6 | Added doc section regarding the CPU's data and instruction interfaces; optimized CPU fetch engine; updated iCE40 synthesis results |
| 20.07.2020 | 1.2.0.5 | Less penalty for taken branches and jumps (2 cycles faster) |
| 19.07.2020 | 1.2.0.0 | CPU bus unit now has independent busses for instruction fetch and data access – merged into single processor bus via new bus switch unit; doubled speed of ALU shifter unit again; all bits of `mcause` CSR can now be modified by application program (full RISC-V-compliant); performance counters CSRs `[m]cycleh` and `[m]instreth` are only 20-bit wide; removed NEORV32-specific custom CSRs – all processor-related information can be obtained from the new `SYSINFO` IO module (CPU is now more independent from processor configuration); changed IO address of `DEVNULL`; fixed bug in bootloader's trap handler; added `USER_CODE` generic to assign a custom user code that can be read by software (from `SYSINFO`) |
| 14.07.2020 | 1.1.0.0 | Added `fence_o` and `fencei_o` signals to top entity to show if a `fence` or `fencei` instruction is executed; added `mvendorid` and `marchid` CSRs (both are always zero); ALU shift unit is faster now; two lowest bits of `mtvec` are always zero; fixed wrong instruction exception priority; removed `HART_ID` generic – `mhartid` CSR is always read as zero; performance counters (`[m]cycle[h]`, `[m]instret[h]` and `time[h]`) are also available in embedded mode – but can be explicitly disabled via the `CSR_COUNTERS_USE` generic; mcause CSR only allows write access to bit 31 and bits 3:0; updated synthesis reports |
| 10.07.2020 | 1.0.6.0 | Non-taken branches are now 1 cycle faster; the `time[h]` CSR now correctly reflects the system time from the MTIME unit; fixed WFI instruction permanently stalling the CPU; `[m]cycle[h]` counters now stop counting when CPU is in sleep mode; `minstret[h]` and `mcycle[h]` now also allow write-access |
| 09.07.2020 | 1.0.5.0 | `X` flag of `misa` CSR is zero now; the default SPI flash boot address of the bootloader is now `0x0080000`; new exemplary FPGA utilization results for Intel, Lattice and Xilinx; `misa` CSR is read-only again, switching compressed extension on/off is pretty bad for the fetch engine; `mtval` and `mcause` CSRs now allow write accesses and are finally RISC-V-compliant; time low and high registers of `MTIME` peripheral can now also be written by user; `MTIME` registers only allow full-word write accesses |
| 06.07.2020 | 1.0.1.0 | Added missing `fence` instruction; added new generic to enable optional Zifencei CPU extension for instruction stream synchronization |
| 05.07.2020 | 1.0.0.0 | New CPU architecture: Fetch and execute engines; increased CPI; timer and counter CSRs are now all 64-bit wide; :warning: fixed CSR access errors; fixed `C.LW` decompression logic; `misa` flags `C` and `M` are now r/w – compressed mode and multiplier/divider support can be switched on/off during runtime; PC(0) is now always zero; :warning: fixed bug in multiplier/divider co-processor; renamed SPI signals; added RISC-V compliance check information – processor now passes the official RISC-V compliance tests |
| 25.06.2020 | 0.0.2.5 | Added `DEVNULL` device; added chapter regarding processor simulation; fixed/added links; fixed typos; added FPGA implementation results for iCE40 UP |
| 23.06.2020 | [**:rocket:0.0.2.3**](https://github.com/stnolting/neorv32/releases/tag/v1.2.0.5) | Publication |