Association table -- half cell

[sporniket]

The principles :

• There is a limited pool of tag, e.g. 0 to 7
• When requesting a tag for a value V :
  • IF V is already bound to a tag, THEN that tag is returned
  • ELSE IF the pool has unused tags, binds V to a free tag that is returned
  • ELSE a not recently requested tag is unbound from it's value, bound to V and returned

[sporniket]

enum HalfCellMode:
  TAG_FROM_VALUE,
  VALUE_FROM_TAG

enum HiReadLoWrite:
  WRITE,
  READ

class HalfCell(Elaboratable):
  __init__(self, valueShape: Shape, tag:Signal (?), mode:HalfCellMode ):
    self.value = Signal(valueShape)
    self.tag = tag
    self.mode = mode
    self.Matches = Signal(1)
    self.DataOut = mode == TAG_FROM_VALUE ? Signal(tag.shape) : Signal(valueShape)
    self DataIn = mode == VALUE_FROM_TAG ? Signal(tag.shape) : Signal(valueShape)

  ports:
    return [self.DataIn, self.RxW, self.DataOut, self.Matches]