Introduction
The (Wishbone)[] bus is an open standard for interconnecting IP cores toghether. The wishbone supports:
- pipelined comunication between IPs
- burst
- optional tags
Wishbone transactions
Classic
Pipelined
Introduction
Configuration and instanciation
The Wishbone Bundle has a construction argument WishboneConfig. For more information the Wishbone spec could be find there.
case class WishboneConfig(
val addressWidth : Int,
val dataWidth : Int,
val selWidth : Int = 0,
val useSTALL : Boolean = false,
val useLOCK : Boolean = false,
val useERR : Boolean = false,
val useRTY : Boolean = false,
val useCTI : Boolean = false,
val tgaWidth : Int = 0,
val tgcWidth : Int = 0,
val tgdWidth : Int = 0,
val useBTE : Boolean = false
){
def useTGA = tgaWidth > 0
def useTGC = tgcWidth > 0
def useTGD = tgdWidth > 0
def useSEL = selWidth > 0
def isPipelined = useSTALL
def pipelined : WishboneConfig = this.copy(useSTALL = true)
def withDataTag(size : Int) : WishboneConfig = this.copy(tgdWidth = size)
def withAddressTag(size : Int) : WishboneConfig = this.copy(tgaWidth = size)
def withCycleTag(size : Int) : WishboneConfig = this.copy(tgdWidth = size)
def withCycleTypeIdentifier : WishboneConfig = this.copy(useCTI = true)
def withBurstType : WishboneConfig = this.copy(useCTI = true, useBTE = true)
}
This configuration object has also some functions to provide some WishboneConfig templates :
| Name | Return | Description |
|---|---|---|
| pipelined | WishboneConfig | Return a wishbone configuration that support pipelined transaction |
| withDataTag(size : Int) | WishboneConfig | Return a wishbone configuration with data tag of specidied size |
| withAddressTag(size : Int) | WishboneConfig | Return a wishbone configuration with address tag of specidied size |
| withCycleTag(size : Int) | WishboneConfig | Return a wishbone configuration with cycle tag of specidied size |
| withCycleTypeIdentifier | WishboneConfig | Return a wishbone configuration with type identifier enabled |
| withBurstType | WishboneConfig | Return a wishbone configuration with type identifier enabled |
You can check the bus configuration with:
| Name | Return | Description |
|---|---|---|
| useTGA | Boolean | Return true if the address tag line is used |
| useTGC | Boolean | Return true if the cycle tag line is used |
| useTGD | Boolean | Return true if the data tag lines are used |
| useSEL | Boolean | Return true if the selection line is used |
| useSTALL | Boolean | Return true if the stall line is used (same as isPipelined) |
| useLOCK | Boolean | Return true if the lock line is used |
| useERR | Boolean | Return true if the error line is used |
| useRTY | Boolean | Return true if the retry line is used |
| useCTI | Boolean | Return true if the Cycle Type Identifie tag line is used |
| useBTE | Boolean | Return true if the Burst Type Extension tag line is used |
| isPipelined | Boolean | Return true if the bus support pipelined interfacing (same as use STALL) |
// You can define it in this way
val myWishboneConfig1 = WishboneConfig(
addressWidth = 8,
dataWidth = 16,
useSTALL = true
)
// Or you can define it in this way
val myWishboneConfig2 = WishboneConfig(8,16).pipelined
// you can create a wishbone bus in this way
val wb = Wishbone(myWishboneConfig2)
// You can check the configuration like this
wb.config.isPipelined // will return true
wb.config.dataWidth //will return 8