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Add in a SimJTAG to connect to OpenOCD's remote-bitbang interface.

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This is simpler than JTAGVPI and is supported better by Verilor.
It is also the same thing Spike uses.
This commit is contained in:
Megan Wachs
2017-04-11 20:03:34 -07:00
parent 206892899f
commit e82328336e
9 changed files with 430 additions and 23 deletions
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79
vsrc/SimJTAG.v Normal file
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// See LICENSE.SiFive for license details.
import "DPI-C" function int jtag_tick
(
output bit jtag_TCK,
output bit jtag_TMS,
output bit jtag_TDI,
output bit jtag_TRSTn,
input bit jtag_TDO
);
module SimJTAG #(
parameter TICK_DELAY = 50
)(
input clock,
input reset,
input enable,
input init_done,
output jtag_TCK,
output jtag_TMS,
output jtag_TDI,
output jtag_TRSTn,
input jtag_TDO_data,
input jtag_TDO_driven,
output [31:0] exit
);
reg [31:0] tickCounterReg;
wire [31:0] tickCounterNxt;
assign tickCounterNxt = (tickCounterReg == 0) ? TICK_DELAY : (tickCounterReg - 1);
bit r_reset;
wire [31:0] random_bits = $random;
wire #0.1 __jtag_TDO = jtag_TDO_driven ?
jtag_TDO_data : random_bits[0];
bit __jtag_TCK;
bit __jtag_TMS;
bit __jtag_TDI;
bit __jtag_TRSTn;
int __exit;
assign #0.1 jtag_TCK = __jtag_TCK;
assign #0.1 jtag_TMS = __jtag_TMS;
assign #0.1 jtag_TDI = __jtag_TDI;
assign #0.1 jtag_TRSTn = __jtag_TRSTn;
assign #0.1 exit = __exit;
always @(posedge clock) begin
r_reset <= reset;
if (reset || r_reset) begin
__exit = 0;
tickCounterReg <= TICK_DELAY;
end else begin
if (enable && init_done) begin
tickCounterReg <= tickCounterNxt;
if (tickCounterReg == 0) begin
__exit = jtag_tick(
__jtag_TCK,
__jtag_TMS,
__jtag_TDI,
__jtag_TRSTn,
__jtag_TDO);
end
end // if (enable && init_done)
end // else: !if(reset || r_reset)
end // always @ (posedge clock)
endmodule