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PicoSoC - A simple example SoC using PicoRV32
=============================================
This is a simple PicoRV32 example design that can run code directly from an SPI
flash chip. This example design uses the Lattice iCE40-HX8K Breakout Board.
The flash is mapped to the memory region starting at 0x01000000. The reset
vector is set to 0x01100000, i.e. at the 1MB offset inside the flash memory.
A small scratchpad memory (default 256 words, i.e. 1 kB) is mapped to address
0x00000000.
Run `make test` to run the test bench (and create `testbench.vcd`).
Run `make prog` to build the configuration bit-stream and firmware images
and upload them to a connected iCE40-HX8K Breakout Board.
| File | Description |
| ----------------------------- | --------------------------------------------------------------- |
| [picosoc.v](picosoc.v) | Top-level PicoSoC Verilog module |
| [picosoc.v](picosoc.v) | Top-level PicoSoC Verilog module |
| [spimemio.v](spimemio.v) | Memory controller that interfaces to external SPI flash |
| [spiflash.v](spiflash.v) | Simulation model of an SPI flash (used by testbench.v) |
| [testbench.v](testbench.v) | Simple test bench for the design (requires firmware.hex). |
| [firmware.s](firmware.s) | Assembler source for firmware.hex/firmware.bin. |
| [hx8kdemo.v](hx8kdemo.v) | FPGA-based example implementation on iCE40-HX8K Breakout Board |
| [hx8kdemo.pcf](hx8kdemo.pcf) | Pin constraints for implementation on iCE40-HX8K Breakout Board |
### Memory map:
| Address Range | Description |
| ------------------------ | --------------------------------------- |
| 0x00000000 .. 0x00FFFFFF | Internal SRAM |
| 0x01000000 .. 0x01FFFFFF | External Serial Flash |
| 0x02000000 .. 0x02000003 | SPI Flash Controller Config Register |
| 0x03000000 .. 0x00FFFFFF | Memory mapped user peripherals |
The example design (hx8kdemo.v) and generic test bench (testbench.v) have 32
GPIO pins mapped to the 32 bit word at address 0x03000000.
### SPI Flash Controller Config Register:
| Bit(s) | Description |
| -----: | --------------------------------------------------------- |
| 31 | MEMIO Enable (reset=1, set to 0 to bit bang SPI commands) |
| 30:20 | Reserved (read 0) |
| 19:16 | IO Output enable bits in bit bang mode |
| 15:14 | Reserved (read 0) |
| 13 | Chip select (CS) line in bit bang mode |
| 12 | Serial clock line in bit bang mode |
| 11:8 | IO data bits in bit bang mode |
| 7 | Reserved (read 0) |
| 6 | DDR Enable bit (reset=0) |
| 5 | QSPI Enable bit (reset=0) |
| 4 | Continous Read Enable bit (reset=0) |
| 3:0 | Number of QSPI dummy cycles (reset=0) |
|
