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hp-saturn/saturn_hp48gx_sysram.v
Raphael Jacquot dd9faf509e initialize ram with random crap
2019-03-18 07:33:24 +01:00

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/*
(c) Raphaël Jacquot 2019
This file is part of hp_saturn.
hp_saturn is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
any later version.
hp_saturn is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with Foobar. If not, see <https://www.gnu.org/licenses/>.
*/
`default_nettype none
`include "saturn_def_buscmd.v"
module saturn_hp48gx_sysram (
i_clk,
i_clk_en,
i_reset,
`ifdef SIM
i_phase,
// i_phases,
i_cycle_ctr,
`endif
i_phase_0,
i_debug_cycle,
i_bus_clk_en,
i_bus_is_data,
o_bus_nibble_out,
i_bus_nibble_in,
i_bus_daisy,
o_bus_daisy,
o_bus_active
);
input wire [0:0] i_clk;
input wire [0:0] i_clk_en;
input wire [0:0] i_reset;
`ifdef SIM
input wire [1:0] i_phase;
//input wire [3:0] i_phases;
input wire [31:0] i_cycle_ctr;
`endif
input wire [0:0] i_phase_0;
input wire [0:0] i_debug_cycle;
/**************************************************************************************************
*
* bus I/O
*
*************************************************************************************************/
input wire [0:0] i_bus_clk_en;
input wire [0:0] i_bus_is_data;
output reg [3:0] o_bus_nibble_out;
input wire [3:0] i_bus_nibble_in;
input wire [0:0] i_bus_daisy;
output wire [0:0] o_bus_daisy;
output wire [0:0] o_bus_active;
/**************************************************************************************************
*
* address handling
*
*************************************************************************************************/
`define SYSRAM_BITS 18
reg [3:0] sysram_data[0:(2** `SYSRAM_BITS) - 1];
reg [3:0] last_cmd;
reg [2:0] addr_pos_ctr;
reg [19:0] local_pc;
reg [19:0] local_dp;
reg [0:0] pc_active;
reg [0:0] dp_active;
reg [3:0] read_nibble;
reg [0:0] exec_write;
reg [3:0] write_nibble;
reg [`SYSRAM_BITS-1:0] write_addr;
reg [0:0] base_conf;
reg [0:0] length_conf;
reg [19:0] base_addr;
reg [19:0] length;
initial begin
last_cmd = 4'b0;
addr_pos_ctr = 3'b0;
local_pc = 20'b0;
local_dp = 20'b0;
pc_active = 1'b0;
dp_active = 1'b0;
read_nibble = 4'b0;
exec_write = 1'b0;
write_nibble = 4'b0;
write_addr = {`SYSRAM_BITS{1'b0}};
base_conf = 1'b0;
length_conf = 1'b0;
base_addr = 20'b0;
length = 20'b0;
`ifdef SIM
/* initialize ram to random crap, just like in the fpga */
for(local_pc = (2**`SYSRAM_BITS)-1; local_pc != 20'hFFFFF; local_pc = local_pc - 20'h1)
sysram_data[local_pc] = $urandom%15;
`endif
end
/*
* testing for read
*/
wire [0:0] do_pc_read = (last_cmd == `BUSCMD_PC_READ);
wire [0:0] do_dp_read = (last_cmd == `BUSCMD_DP_READ);
wire [0:0] do_read = do_pc_read || do_dp_read;
/*
* testing for write
*/
wire [0:0] do_pc_write = (last_cmd == `BUSCMD_PC_WRITE);
wire [0:0] do_dp_write = (last_cmd == `BUSCMD_DP_WRITE);
wire [0:0] do_write = do_pc_write || do_dp_write;
/*
* accessing the ioram
*/
wire [0:0] configured = length_conf && base_conf;
assign o_bus_daisy = configured;
wire [0:0] use_pc = do_pc_read || do_pc_write;
wire [0:0] use_dp = do_dp_read || do_dp_write;
wire [19:0] above_addr = base_addr + length;
wire [0:0] active = ((pc_active && use_pc) || (dp_active && use_dp)) && configured;
assign o_bus_active = active;
wire [19:0] pointer = use_pc?local_pc:local_dp;
wire [19:0] access_pointer = pointer - base_addr;
wire [`SYSRAM_BITS-1:0] address = access_pointer[`SYSRAM_BITS-1:0];
wire [0:0] gen_active = i_clk_en && !i_debug_cycle && i_phase_0 && (do_read || do_write);
wire [0:0] pre_read = i_clk_en && i_phase_0 && !i_debug_cycle && do_read & active;
wire [0:0] can_read = i_bus_clk_en && i_bus_is_data && do_read && active;
wire [0:0] can_write = i_bus_clk_en && i_bus_is_data && do_write && active;
/**************************************************************************************************
*
* reading and writing to system ram
*
*************************************************************************************************/
/**************************************************************************************************
*
* generate the active signals
* these comparisons incur important delays, so they're done on a clock cycle
*
*************************************************************************************************/
always @(posedge i_clk) begin
if (gen_active) begin
pc_active <= (local_pc >= base_addr) && (local_pc < above_addr);
dp_active <= (local_dp >= base_addr) && (local_dp < above_addr);
end
if (i_reset) begin
pc_active <= 1'b0;
dp_active <= 1'b0;
end
end
/**************************************************************************************************
*
* read from the system ram in a pipelined fashion
*
*************************************************************************************************/
always @(posedge i_clk) begin
if (pre_read) begin
`ifdef SIM
$display("RAM-GX %0d: [%d] pre_read %h <= sysram[%5h]", i_phase, i_cycle_ctr, sysram_data[address], address);
`endif
read_nibble <= sysram_data[address];
end
end
always @(posedge i_clk) begin
if (can_read) begin
`ifdef SIM
$display("RAM-GX %0d: [%d] do_read %h <= sysram[%5h]", i_phase, i_cycle_ctr, read_nibble, address);
`endif
o_bus_nibble_out <= read_nibble;
end
end
/**************************************************************************************************
*
* write to the system ram, this is pipelined so gain some speed
*
*************************************************************************************************/
always @(posedge i_clk) begin
if (can_write) begin
`ifdef SIM
$display("RAM-GX %0d: [%d] pre_write sysram[%5h] <= %h", i_phase, i_cycle_ctr, address, i_bus_nibble_in);
`endif
write_nibble <= i_bus_nibble_in;
write_addr <= address;
exec_write <= 1'b1;
end
if (exec_write)
exec_write <= 1'b0;
end
always @(posedge i_clk) begin
if (exec_write) begin
`ifdef SIM
$display("RAM-GX %0d: [%d] do_write sysram[%5h] <= %h", i_phase, i_cycle_ctr, write_addr, write_nibble);
`endif
sysram_data[write_addr] <= write_nibble;
end
end
/**************************************************************************************************
*
* generate length and base address for configure
*
*************************************************************************************************/
`ifdef SIM
wire [3:0] imm_nibble = sysram_data[address];
`endif
/* generate length */
reg [19:0] new_length;
always @(*) begin
case (addr_pos_ctr)
3'd0: new_length = { 16'b0, i_bus_nibble_in };
3'd1: new_length = { 12'b0, i_bus_nibble_in, length[ 3:0] };
3'd2: new_length = { 8'b0, i_bus_nibble_in, length[ 7:0] };
3'd3: new_length = { 4'b0, i_bus_nibble_in, length[11:0] };
3'd4: new_length = { i_bus_nibble_in, length[15:0] };
default: new_length = 20'b0;
endcase
end
/* generate length */
reg [19:0] new_base_addr;
always @(*) begin
case (addr_pos_ctr)
3'd0: new_base_addr = { 16'b0, i_bus_nibble_in };
3'd1: new_base_addr = { 12'b0, i_bus_nibble_in, base_addr[ 3:0] };
3'd2: new_base_addr = { 8'b0, i_bus_nibble_in, base_addr[ 7:0] };
3'd3: new_base_addr = { 4'b0, i_bus_nibble_in, base_addr[11:0] };
3'd4: new_base_addr = { i_bus_nibble_in, base_addr[15:0] };
default: new_base_addr = 20'b0;
endcase
end
/*
* general case
*/
always @(posedge i_clk) begin
if (i_bus_clk_en && i_clk_en) begin
if (i_bus_is_data) begin
/* do things with the bits...*/
case (last_cmd)
`BUSCMD_PC_READ:
begin
// o_bus_nibble_out <= rom_data[local_pc[`ROMBITS-1:0]];
local_pc <= local_pc + 1;
end
`BUSCMD_DP_READ:
begin
// o_bus_nibble_out <= rom_data[local_dp[`ROMBITS-1:0]];
local_dp <= local_dp + 1;
end
`BUSCMD_PC_WRITE: local_pc <= local_pc + 1;
`BUSCMD_DP_WRITE: local_dp <= local_dp + 1;
`BUSCMD_LOAD_PC:
begin
local_pc[addr_pos_ctr*4+:4] <= i_bus_nibble_in;
addr_pos_ctr <= addr_pos_ctr + 3'd1;
end
`BUSCMD_LOAD_DP:
begin
local_dp[addr_pos_ctr*4+:4] <= i_bus_nibble_in;
addr_pos_ctr <= addr_pos_ctr + 3'd1;
end
`BUSCMD_CONFIGURE:
if (i_bus_daisy) begin
if (!length_conf && !base_conf) length <= new_length;
if (length_conf && !base_conf) base_addr <= new_base_addr;
addr_pos_ctr <= addr_pos_ctr + 3'd1;
end
default: begin end
endcase
/* auto switch to pc read / dp read */
if (addr_pos_ctr == 4) begin
case (last_cmd)
`BUSCMD_LOAD_PC: last_cmd <= `BUSCMD_PC_READ;
`BUSCMD_LOAD_DP: last_cmd <= `BUSCMD_DP_READ;
`BUSCMD_CONFIGURE:
begin
if (!length_conf && !base_conf)
begin
length_conf <= 1'b1;
length <= ~new_length + 20'b1;
`ifdef SIM
$display("RAM-GX %0d: [%d] configure length %5h => %5h", i_phase, i_cycle_ctr, new_length, ~new_length + 20'b1);
`endif
end
if (length_conf && !base_conf)
begin
base_conf <= 1'b1;
`ifdef SIM
$display("RAM-GX %0d: [%d] configure base_addr %5h", i_phase, i_cycle_ctr, new_base_addr);
`endif
end
end
default: begin end
endcase
end
`ifdef SIM
$write("RAM-GX %0d: [%d] ", i_phase, i_cycle_ctr);
case (last_cmd)
`BUSCMD_PC_READ:
begin
$write("PC_READ ");
if (configured)
begin
if (active) $write("<= sysram[%5h]: %h", local_pc, imm_nibble);
else $write("inactive");
end
else $write("(unconfigured)");
end
`BUSCMD_DP_READ:
begin
$write("DP_READ ");
if (configured)
begin
if (active) $write("<= sysram[%5h]: %h", local_dp, imm_nibble);
else $write("(inactive)");
end
else $write("(unconfigured)");
end
`BUSCMD_DP_WRITE:
begin
$write("DP_WRITE ");
if (configured)
begin
if (active) $write("sysram[%5h] <= %h", local_dp, i_bus_nibble_in);
else $write("(inactive %h)", i_bus_nibble_in);
end
else $write("(ignore)");
end
`BUSCMD_LOAD_PC: $write("LOAD_PC - pc %5h, %h pos %0d", local_pc, i_bus_nibble_in, addr_pos_ctr);
`BUSCMD_LOAD_DP: $write("LOAD_DP - dp %5h, %h pos %0d", local_dp, i_bus_nibble_in, addr_pos_ctr);
`BUSCMD_CONFIGURE:
begin
$write("CONFIGURE - ");
if (!configured)
begin
if (!length_conf) $write("length %5h", new_length);
else $write("base_addr %5h", new_base_addr);
$write(", %h pos %0d", i_bus_nibble_in, addr_pos_ctr);
end
else $write("already done, ignore");
end
`BUSCMD_RESET: $write("RESET");
default: $write("last_command %h nibble %h - UNHANDLED", last_cmd, i_bus_nibble_in);
endcase
if (addr_pos_ctr == 4) begin
case (last_cmd)
`BUSCMD_LOAD_PC: $write(" auto switch to PC_READ");
`BUSCMD_LOAD_DP: $write(" auto switch to DP_READ");
default: begin end
endcase
end
$write("\n");
`endif
end else begin
last_cmd <= i_bus_nibble_in;
if ((i_bus_nibble_in == `BUSCMD_LOAD_PC) || (i_bus_nibble_in == `BUSCMD_LOAD_DP))
addr_pos_ctr <= 0;
if (i_bus_nibble_in == `BUSCMD_CONFIGURE)
addr_pos_ctr <= 3'd0;
if (i_bus_nibble_in == `BUSCMD_RESET)
begin
base_addr <= 20'b0;
base_conf <= 1'b0;
length <= 20'b0;
length_conf <= 1'b0;
end
`ifdef SIM
$write("RAM-GX %0d: [%d] ", i_phase, i_cycle_ctr);
case (i_bus_nibble_in)
`BUSCMD_PC_READ: $write("PC_READ");
`BUSCMD_DP_READ: $write("DP_READ");
`BUSCMD_DP_WRITE: $write("DP_WRITE");
`BUSCMD_LOAD_PC: $write("LOAD_PC");
`BUSCMD_LOAD_DP: $write("LOAD_DP");
`BUSCMD_CONFIGURE: $write("CONFIGURE");
`BUSCMD_RESET: $write("RESET base_addr to %5h and unconfigure", 20'h0);
default: begin end
endcase
$write("\n");
`endif
end
end
if (i_reset) begin
last_cmd <= 4'b0;
addr_pos_ctr <= 3'b0;
local_pc <= 20'b0;
local_dp <= 20'b0;
pc_active <= 1'b0;
dp_active <= 1'b0;
read_nibble <= 4'b0;
write_nibble <= 4'b0;
base_conf <= 1'b0;
length_conf <= 1'b0;
base_addr <= 20'b0;
length <= 20'b0;
end
end
// Verilator lint_off UNUSED
wire [(19 -`SYSRAM_BITS):0] unused = { access_pointer[19:`SYSRAM_BITS] };
// Verilator lint_on UNUSED
endmodule
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