Let’s imagine a component that converts an RGB color into a gray one, and then writes it into external memory.
| io name | Direction | Description |
|---|---|---|
| clear | in | Clear all internal registers |
| r,g,b | in | Color inputs |
| wr | out | Memory write |
| address | out | Memory address, incrementing each cycle |
| data | out | Memory data, gray level |
class RgbToGray extends Component{
val io = new Bundle{
val clear = in Bool
val r,g,b = in UInt(8 bits)
val wr = out Bool
val address = out UInt(16 bits)
val data = out UInt(8 bits)
}
def coef(value : UInt,by : Float) : UInt = (value * U((255*by).toInt,8 bits) >> 8)
val gray = RegNext(
coef(io.r,0.3f) +
coef(io.g,0.4f) +
coef(io.b,0.3f)
)
val address = CounterFreeRun(stateCount = 1 << 16)
io.address := address
io.wr := True
io.data := gray
when(io.clear){
gray := 0
address.clear()
io.wr := False
}
}