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// See LICENSE for license details.
package midas.targetutils.xdc
import chisel3.experimental.ChiselAnnotation
import firrtl.annotations.ReferenceTarget
sealed trait RAMStyle
* Some rough guidance, based on Ultrascale+, is provided in the scala doc for
* each hint. Consult the Xilinx UGs for your target architecture and the
* synthesis UG (UG901).
object RAMStyles {
* From UG901 (v2020.2): Instructs the tool to use the UltraScale+ URAM primitives.
* URAMs are 288Kb, 72b wide, 4096 deep.
case object ULTRA extends RAMStyle
* From UG901 (v2020.2): Instructs the tool to infer RAMB type components
* In Ultrascale+ (and older families), BRAMs are 36Kb, and have flexible aspect
* ratio: 1b x 64K to 72b x 512
case object BRAM extends RAMStyle
/** From UG901 (v2020.2): Instructs the tool to infer registers instead of RAMs. */
case object REGISTERS extends RAMStyle
/** From UG901 (v2020.2): Instructs the tool to infer the LUT RAMs. */
case object DISTRIBUTED extends RAMStyle
/** Introduced in v2020.2. From UG901 (v2020.2):
* Instructs the tool to infer a combination of RAM types designed to minimize the
* amount of space that is unused.
* Note: This should probably be avoided for non-emulation-class
* FPGAs (e.g., VU19P), which tend to have rich embedded memory resources, as
* these designs tend to be under heavy LUT pressure. Here sparsely using
* BRAM / URAM resources insead of a space-optimal hybrid is desirable.
case object MIXED extends RAMStyle
object RAMStyleHint {
// _reg suffix is applied to memory cells by Vivado, the glob manages
// duplication for multibit memories.
private [midas] def propertyTemplate(style: RAMStyle): String =
s"set_property RAM_STYLE ${style} [get_cells {}_reg*]"
private def annotate(style: RAMStyle, rT: =>ReferenceTarget): Unit = {
chisel3.experimental.annotate(new ChiselAnnotation {
def toFirrtl = XDCAnnotation(
* Annotates a chisel3 Mem indicating it should be implemented with a particular
* Xilinx RAM structure.
def apply(mem: chisel3.MemBase[_], style: RAMStyle): Unit = {
annotate(style, mem.toTarget)