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Summary

This project is an SOC (System on a Chip) coded in VHDL and implemented for the Lattice iCE40-hx8k dev board. The SOC contains the following components: Nova CPU + RAM + UART + Timer + I/O Ports

Required Hardware

  • Lattice iCE40-hx8k dev board (can be ordered online at www.latticesemi.com)
  • USB-to-Serial 3.3V adapter (can be ordered from eBay)
  • misc USB cables and wires for connecting the USB-to-Serial adapter

NOTE: Make sure the USB-to-serial adapter is a 3.3V version. Some adapters have 5V interface signals which could damage your iCE40-hx8k dev board.

Tools

  • IceCube2 (from Lattice Semiconductor) was used for synthesis and FPGA Routing.
  • Icestorm (https:/github.com/cliffordwolf/icestorm) was used for programming.

Build Flow

I used the Lattice IceCube2 software to generate the SOC_bitmap.bin programming file and then I used this command line "iceprog SOC_bitmap.bin" the program the iCE40-hx8k dev board over the USB cable (iceprog is part of the icestorm tool suite).

Console Interface

I used the minicom program (on Ubuntu Linux) as a console to communicate with the SOC over the USB-to-Serial connection. Configure minicom using the command line "minicom -s" to configure the serial port for ttyUSB0 and turn of the hardware handshaking. There are probably other alternatives to minicom. Any ANSI terminal-emulator program should work for this application.

Pinout

The iCE40 pins are defined as follows:

UART_RXD   G1 -pullup yes
UART_TXD   G2
PORTA[0]   B5
PORTA[1]   B4
PORTA[2]   A2
PORTA[3]   A1
PORTA[4]   C5
PORTA[5]   C4
PORTA[6]   B3
PORTA[7]   C3
RESET      N3 -pullup yes
CLK        J3 -pullup yes

Memory Map

The memory map (in octal) of this SOC is as follows:

0 -> 17777  8k words RAM

I/O Map

The I/O map (in octal) of this SOC is as follows:

10 -> 17  UART  registers
20 -> 21  Timer registers
22        Output register
23        Interrupt mask register
24 -> 25  Random number generator
26        Interrupt source register

Nova CPU Background Info

The Nova series was an extremely successful and influential family of machines from Data General. The first Nova was introduced in 1969 and the Nova series (Nova-800, Nova-1200, Supernova, Nova-3 and Nova-4) continued through the mid 1980's. It's main claim to fame was it's simplicity both in its architecture and its implementation (the first Nova CPU was implemented on a single 15"x15" circuit board). The CPU in this SOC implements the base Nova-4 features (no floating point and no memory management).

Contributors

  • Scott L Baker - SOC design

License

See the LICENSE file in this repository