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).

:information_source: To see a list of all commits
between release run `git log v1.4.7.0..v1.4.8.0` (example to to see commits between v1.4.7.0 and v1.4.8.0).

:information_source: The processor can determine it's version from the `mimpid` CSR (at CSR address 0xf13). A 8x4-bit BCD representation is used. Leading
zeros are optional. Example: `CSR(mimpid) = 0x01040312 => 01.04.03.12 = Version 01.04.03.12 = v1.4.3.12`. 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 |
|:----------:|:-------:|:--------|
| 17.01.2021 | 1.5.0.3 | CPU data register file can now be mapped to a **single** "true dual-port" block RAM by the synthesizer (requiring only 1024 memory bits instead of 2048); :bug: fixed typo error in `sim/rtl_modules/neorv32_imem.vhd`; modified `M` co-processor (due to register file read access modification), reduced switching activity when co-processor is idle; logic/arithmetic operations of `B` extension only require 3 cycles now, reduced switching activity when co-processor is idle |
| 15.01.2021 | 1.5.0.2 | added instruction cache associativity configuration (number of sets); new configuration generic: `ICACHE_ASSOCIATIVITY` -> number of sets (1 = direct mapped, 2 = 2-way set-associative), has to be a power of two; if associativity is > 1 the used replacement policy is *least recently used (LRU)*; :bug: fixed bug in `sw/lib/source/neorv32_cpu.c` PMP.CFG configuration function |
| 14.01.2021 | 1.5.0.1 | added new HPM trigger event: multi-cycle ALU operation wait cycle (`HPMCNT_EVENT_WAIT_MC`); renamed `neorv32_cache.vhd` -> `neorv32_icache.vhd` |
| 10.01.2021 | [**:rocket:1.5.0.0**](https://github.com/stnolting/neorv32/releases/tag/v1.5.0.0) | Renamed configuration generics: `*_USE` -> `*_EN` |
| 10.01.2021 | 1.4.9.10 | :sparkles: Added support for [**bit manipulation extension (`B`)**](https://github.com/riscv/riscv-bitmanip) - base subset `Zbb` only (:warning: RISC-V `B` (sub-)extensions are not officially ratified yet; compatible to version "0.94-draft"); enabled via new configuration constant `CPU_EXTENSION_RISCV_B` (default = false); uported `Zbb` instructions: `CLZ` `CTZ` `CPOP` `SEXT.B` `SEXT.H` `MIN[U]` `MAX[U]` `ANDN` `ORN` `XNOR` `ROL` `ROR` `RORI` `zext`(*pseudo-instruction* for `PACK rd, rs, zero`) `rev8`(*pseudo-instruction* for `GREVI rd, rs, -8`) `orc.b`(*pseudo-instruction* for `GORCI rd, rs, 7`); added `B` flag to `misa` CSR; added `Zbb` flag to `mzext` CSR |
| 03.01.2021 | 1.4.9.8 | Added HPM trigger for instruction issue wait cycle (caused by pipeline flush); all HPM counters do not increment if CPU is sleep mode; fixed CoreMark timer overflow issues; `rtl/core/neorv32_busswitch.vhd`: removed wait states, less load/store wait cycles -> faster execution; updated CoreMark results |
| 02.01.2021 | 1.4.9.7 | :sparkles: added RISC-V hardware performance monitors (`HPM`); new CSRs: `mhpmevent*`(3..31), `[m]hpmcounter*[h]`(3..31), amount configurable via top's generic `HPM_NUM_CNTS`; supported counter events: active cycle, retired instruction, retired compressed instruction, instruction fetcch memory wait cycle, load operation, store operation, load/store memory wait cycle, unconditional jump, conditional branche (all), conditional taken branch, entered trap, illegal instruction exception; PMP can now have up to 64 regions; number of regions configured via top's `PMP_NUM_REGIONS` generic; removed obsolete top's `PMP_USE` generic; removed PMP flag from `mzext` CSR; minimal region granularity (in bytes) configured via top's `PMP_MIN_GRANULARITY` generic, has to be a power of two and >= 8 bytes; :bug: fixed bug in sleep (`wfi`) instruction |
| 29.12.2020 | 1.4.9.5 | New UART features: "frame check" (test if stop bit is set), error indicated via `UART_DATA` reg's `UART_DATA_FERR` flag; configurable parity bit (`UART_CT.UART_CT_PMODE1:UART_CT_PMODE0`, 00=no parity; 10=even parity; 11=odd parity); parity error indicated via `UART_DATA` reg's `UART_DATA_PERR` flag; moved UART's RX overrun flag to `UART_DATA.UART_DATA_OVERR` |
| 26.12.2020 | 1.4.9.4 | removed `zicnt_en` option (was used to discard the standard RISC-V counters and timers from implementation); added missing `mcounteren` CSR (to allow read-access from user-level code to `cycle[h]` / `time[h]` / `[m]instret[h]` CSRs); available bits: 0: `CY`, 1: `TM`, 2: `IR`; added missing `mcountinhibit` CSR (to disable auto-increment of `[m]cycle[h]` / `[m]instret[h]` CSRs); available bits: 0: `CY`, 2: `IR`; :warning: renamed CSR bits C-code-aliases: `CPU_*` -> `CSR_*` |
| 25.12.2020 | 1.4.9.3 | Added missing `UBE` flag to `mstatus` CSR, indicates Endianness for load/stores in user mode (always set indicating BIG-endian mode), is a copy of `mstatush.mbe` |
| 23.12.2020 | 1.4.9.2 | :sparkles: added processor-internal instruction cache `rtl/core/neorv32_cache.vhd` (direct mapped); new configuration generics: `ICACHE_USE` (implement cache), `ICACHE_BLOCK_SIZE` (cache block/page/line size), `ICACHE_NUM_BLOCKS` (number of cache blocks); added `SYSINFO_CACHE` register to SYSINFO to check cache configuration by software  |
| 20.12.2020 | 1.4.9.1 | :bug: fixed bug in CPU's instruction fetch engine (alignment_errros/bus_errors were not acknowledged correctly); added `BUS_TIMEOUT` generic to CPU (defines the amount of cycles after which an *unacknowledged* bus access will get terminated and raises a bus access fault exception) |
| 19.12.2020 | [**:rocket:1.4.9.0**](https://github.com/stnolting/neorv32/releases/tag/v1.4.9.0) | Testbench: added memory-mapped triggers to trigger core's "machine software & external interrupts"; `sw/example/cpu_test`: removed CFU tests, added `MEI` and `MSI` tests; added **RISC-V-Compliance Test Framework** to repository (`riscv-compliance/`), core passes all `rv32` tests (riscv-compliance v2.1) |
| 18.12.2020 | 1.4.8.13 | Added additional simulation files: simulation-optimized IMEM-ROM (so far, this is only relevant for the *new* NEORV32 RISC-V Compliance test framework v2.0); **:sparkles: Processor now passes all `rv32` tests of the new [RISC-V Compliance Test Framework v2.0](https://github.com/riscv/riscv-compliance/releases/tag/v2.0) :sparkles:** |
| 16.12.2020 | 1.4.8.12 | :warning: fixed (another) bug in `mtval` CSR generation (wrong value for "breakpoint" trap); updated `mtval` value table in data sheet; fixed bug in load/store operation (intoroduced in version 1.4.8.10) |
| 16.12.2020 | 1.4.8.11 | :warning: fixed bug in `mtval` CSR generation (wrong values for some traps); fixed bug in `mip` CSR (writing zero to implemented bits now actually clears pending interrupts); fixed bug in IRQ priority encoding (machine software interrupt `MSI` comes before machine timer interrupt `MTI`) |
| 12.12.2020 | 1.4.8.10 | :warning: fixed wrong `trap_reset_c` encoding (in it's expanded form it should be 0x80000000) and reset logic: hardware `mcause` register is now set to `trap_reset_c` after a hardware reset; crt0.S start-up code now sets `mcause` to `trap_reset_c` after finishing hardware setup |
| 11.12.2020 | 1.4.8.9 | Added option to exclude standard RISC-V performance counters (`[m]cycle[h]` and `[m]instret[h]`) for size-constrained implementations; disabled by setting VHDL package's `zicnt_en_c` constant to false; software can determine state of `zicnt_en_c` via `mzext` CSR's `CPU_MZEXT_ZICNT` bit; added new signal to processor top entity: `mtime_i`, this signal is used for updateting the `time[h]` CSRs if the processor-internal MTIME unit is disabled (via `IO_MTIME_USE` = `false`) |
| 10.12.2020 | 1.4.8.8 | Added missing `mstatush` CSR (only bit `MBE` is implemented yet); added option to configure external bus interface for BIG- or little-endian byte-order, configured via VHDL package `xbus_big_endian_c` constant, default = BIG-endian, software can check endianness of the interface via SYSINFO's `SYSINFO_FEATURES(SYSINFO_FEATURES_MEM_EXT_ENDIAN)` flag; added `mstatush` CSR and endianness information to data sheet |
| 09.12.2020 | 1.4.8.7 | Added missing *environment call from U-mode* exception (via `ecall` instruction in user-mode); added environment call from U-mode to data sheet |
| 09.12.2020 | 1.4.8.6 | :warning: fixed bugs in ALU's co-processor interface: ATOMIC `A` extension could not be used without MULDIV `M` extension, CPU might have permanently stalled when executing an instruction from a disabled ISA extension; :lock: added security feature: illegal user-level CSR read access will always return zero; added new section *Execution Safety* to neorv32.pdf data sheet |
| 07.12.2020 | 1.4.8.5 | :warning: fixed bug in next-PC logic (introduced with version 1.4.8.1) that caused instruction fetch from memories with more than 1 cycle latency to fail |
| 05.12.2020 | 1.4.8.4 | :warning: fixed bug in physical memory protection (PMP): region size configuration was incorrect; removed `PMP_NUM_REGIONS` and `PMP_GRANULARITY` CPU/processor generics (PMP configuration now via package constants); reworked section *2.4. Instruction Sets and CPU Extensions* of neorv32.pdf |
| 04.12.2020 | 1.4.8.2 | Added PMA (physical memory attribute) to processor-internal IO region: `NO EXECUTE`; added *3.3.Address Space/Physical Memory Attributes (PMAs)* section to neorv32.pdf |
| 03.12.2020 | 1.4.8.1 | Optimized CPU program counter (PC) update logic and "next PC" computation (shortend critical path); updated bootloader (configuration option for direct-boot-from-SPI-flash only) and *customization* text in neorv32.pdf |
| 01.12.2020 | [**:rocket:1.4.8.0**](https://github.com/stnolting/neorv32/releases/tag/v1.4.8.0) | :warning: fixed bug in CPU-internal co-processor interface; optimized multiplier unit (~1 faster); added CPU `A` (atomic) extension support (only `lr.w` and `sc.w` instructions yet); added `lock` signal to CPU and processor's external bus interface |
| 28.11.2020 | 1.4.7.6 | Split ALU core operations: shortened  critical path - replaced ALU output 8:1 mux by a 4:1 mux |
| 26.11.2020 | 1.4.7.5 | Minor rtl clean-up; CSR access instructions are one cycle faster now (3 cycles now); system/environemnt instructions (`ecall` `ebreak` `mret` `wfi`) need one additional cycle (4 cycles now) |
| 25.11.2020 | 1.4.7.4 | :warning: fixed bug in `FENCE.I` instruction that corrupted instruction fetch when executing code from processor-external memory; default testbench (`sim/neorv32_tb.vhd`) now features external IMEM, external DMEM and external IO connected via external bus interface; simulation now allows CPU to execute code using external memories only (no internal IMEM/DMEM); optimized CPU's instruction fetch interface (no more unnecessary transfer cancel requests) |
| 20.11.2020 | 1.4.7.2 | :warning: fixed bug in CPU bus unit that caused a memory exception after reset in some cases; added second simulated external (Wishbone) memory to testbench (one memory for simulating an external IMEM, one memory for simulating external memory-mapped IO); external bus interface (`wishbone`) now makes sure that a canceled bus transfer is really understood by the accessed peripheral |
| 20.11.2020 | 1.4.7.1 | Removed deprecated "update_enable signal" from IMEM |
| 11.11.2020 | [**:rocket:1.4.7.0**](https://github.com/stnolting/neorv32/releases/tag/v1.4.7.0) | Further optimized pipeline front-end: Jumps and branches are one cycle faster (+5% coremark performance); updated synthesis results; updated performance results; added `hello_world` example program |
| 07.11.2020 | 1.4.6.7 | Updated bootloader (size optimization) and changed processor version output; added project logo; minor data sheet edits |
| 03.11.2020 | 1.4.6.6 | Removed SPI module's *buggy* "LSB-first mode", SPI module now always sends data MSB-first; removed SPI.CTRL `SPI_CT_DIR` bit; modfied bit order in SPI CTRL register; updated SPI SW library |
| 02.11.2020 | 1.4.6.5 | :warning: Fixed bug in CPU's illegal instruction detection logic; CPU rtl code optimizations - further reduced hardware footprint; rtl code clean-ups |
| 01.11.2020 | 1.4.6.4 | :warning: Fixed bug in `[m]instret[h]` and `[m]cycle[h]` carry logic; CPU hardware optimizations (area reduction, shortend critical path) |
| 29.10.2020 | 1.4.6.3 | rtl code clean-up; made preparations for additional co-processors |
| 25.10.2020 | 1.4.6.2 | Added tag signal (`wb_tag_o`) to processor's Wishbone bus; removed processors's `priv_o` - privilege level is now encoded in Wishbone *tag* signal; added a more sophisticated **FreeRTOS** example ("full_demo") |
| 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 data sheet; 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 |