我将一些systermverilog代码重写到chisel中,但我找不到在chisel中表达systemverilog的打包联合的好方法。例如,
typedef struct packed {
logic [3:0] version;
logic [3:0] ihl;
logic [7:0] tos;
logic [15:0] total_length;
logic [15:0] id;
logic reserved;
logic df;
logic mf;
logic [12:0] frag_offset;
logic [7:0] ttl;
logic [7:0] protocol;
logic [15:0] checksum;
logic [31:0] ip_sa;
logic [31:0] ip_da;
} ipv4_s;
typedef struct packed {
logic [63:0] DW0;
logic [63:0] DW1;
logic [31:0] DW2;
} common_20b_s;
typedef union packed {
ipv4_s structured;
common_20b_s array;
logic [$bits(ipv4_s)-1:0] bits;
} ipv4_hdr_u;
module test (
input clk,
input [$bits(ipv4_s)-1:0] pkt_stream_in,
input [3:0] mode,
input [127:0] config_in,
output reg [$bits(ipv4_s)-1:0] pkt_stream_out
);
ipv4_hdr_u ipv4_hdr;
always @* begin
ipv4_hdr.bits = pkt_stream_in;
case(mode)
0: ipv4_hdr.structured.ip_sa = config_in[31:0];
1: ipv4_hdr.array.DW0 = config_in[63:0];
endcase
end
always @(posedge clk)
pkt_stream_out <= ipv4_hdr.bits;
endmodule: test
对于ipv4_s
和common_2b_s
这两个数据结构,结构中的每个字段都可以单独更新,但是要凿。有什么办法可以表达这种功能吗?
最佳答案
没有对打包联合的内置支持,但您可以创建自定义类(子类型Bundle
)并自己构建类似的东西。它会导致更多的样板,所以我认为一些内置支持会很好,但它可以完成工作:
可运行音译:https://scastie.scala-lang.org/5jOMpEYuRbu9VbzScvDffQ
粘贴在下面:
import chisel3._
import chisel3.util._
import chisel3.stage.ChiselStage
class IPV4_s extends Bundle {
val version = UInt(4.W)
val ihl = UInt(4.W)
val tos = UInt(8.W)
val total_length = UInt(16.W)
val id = UInt(16.W)
val reserved = Bool()
val df = Bool()
val mf = Bool()
val frag_offset = UInt(13.W)
val ttl = UInt(8.W)
val protocol = UInt(8.W)
val checksum = UInt(16.W)
val ip_sa = UInt(32.W)
val ip_da = UInt(32.W)
}
object IPV4_s {
// Utility, I got sick of typing this righthand expression
val width = (new IPV4_s).getWidth
}
class Common_20b_s extends Bundle {
val DW0 = UInt(64.W)
val DW1 = UInt(64.W)
val DW2 = UInt(32.W)
}
class IPV4_hdr_u extends Bundle {
val bits = UInt(IPV4_s.width.W)
// These helpers aren't really necessary but can save some typing
def asIPV4_s = this.asTypeOf(new IPV4_s)
def asCommon_20b_s = this.asTypeOf(new Common_20b_s)
}
class Test extends MultiIOModule {
// clock is inherited
val pkt_stream_in = IO(Input(new IPV4_hdr_u))
val mode = IO(Input(UInt(4.W)))
val config_in = IO(Input(UInt(128.W)))
val pkt_stream_out = IO(Output(new IPV4_hdr_u))
// Default to using stream_in
val ipv4_hdr = WireInit(pkt_stream_in)
switch (mode) {
is (0.U) {
// Cast input and use temporary for subfield assignment
val t = WireInit(pkt_stream_in.asIPV4_s)
t.ip_sa := config_in(31, 0)
ipv4_hdr := t.asTypeOf(new IPV4_hdr_u)
}
is (1.U) {
val t = WireInit(pkt_stream_in.asCommon_20b_s)
t.DW0 := config_in(63, 0)
ipv4_hdr := t.asTypeOf(new IPV4_hdr_u)
}
}
pkt_stream_out := ipv4_hdr
}
关于chisel - chisel 中的 systemverilog 联合类型,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/62112755/