spi/README.md

Verilog SPI

Verilog SPI master and slave that supports all modes and variable width via parameters.

License

This Program is subject to the terms of the Mozilla Public License, v.2.0. A copy of this license may be found in the file COPYING. You can obtain one at https://mozilla.org/MPL/2.0/.

Tests

Go into tests and run make. To rerun tests, run make clean followed by make.

The test for each mode generates a .vcd file which you may view using GTKWave. You can use this to gauge which SPI mode is appropriate for your device.

SPI Modes

Modes are denoted by modePH, where P is the polarity (0 for normal, 1 for inverted) and H for phase:

• H = 0 means the device reads on a rising edge and writes on a falling edge.
• H = 1 means the device reads on a falling edge and writes on a rising edge.

Although these modules support all SPI modes, they are labeled slightly differently from other SPI modes. The phase factor is denoted in terms of falling and rising edges, not in terms of leading and trailing edges. This means that polarity also flips the phase term, so a mode 3 device is a mode 10 device. Devices with regular clock polarity are unaffected, so a mode 0 device is a mode 00 device, and a mode 1 device is a mode 01 device.