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/trunk/rtl/core/tv80n.v
0,0 → 1,182
//
// TV80 8-Bit Microprocessor Core
// Based on the VHDL T80 core by Daniel Wallner (jesus@opencores.org)
//
// Copyright (c) 2004 Guy Hutchison (ghutchis@opencores.org)
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the "Software"),
// to deal in the Software without restriction, including without limitation
// the rights to use, copy, modify, merge, publish, distribute, sublicense,
// and/or sell copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
// IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
// CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
// TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
// SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 
// Negative-edge based wrapper allows memory wait_n signal to work
// correctly without resorting to asynchronous logic.
 
module tv80n (/*AUTOARG*/
// Outputs
m1_n, mreq_n, iorq_n, rd_n, wr_n, rfsh_n, halt_n, busak_n, A, do,
// Inputs
reset_n, clk, wait_n, int_n, nmi_n, busrq_n, di
);
 
parameter Mode = 0; // 0 => Z80, 1 => Fast Z80, 2 => 8080, 3 => GB
parameter T2Write = 0; // 0 => wr_n active in T3, /=0 => wr_n active in T2
parameter IOWait = 1; // 0 => Single cycle I/O, 1 => Std I/O cycle
 
 
input reset_n;
input clk;
input wait_n;
input int_n;
input nmi_n;
input busrq_n;
output m1_n;
output mreq_n;
output iorq_n;
output rd_n;
output wr_n;
output rfsh_n;
output halt_n;
output busak_n;
output [15:0] A;
input [7:0] di;
output [7:0] do;
 
reg mreq_n;
reg iorq_n;
reg rd_n;
reg wr_n;
reg nxt_mreq_n;
reg nxt_iorq_n;
reg nxt_rd_n;
reg nxt_wr_n;
wire cen;
wire intcycle_n;
wire no_read;
wire write;
wire iorq;
reg [7:0] di_reg;
wire [6:0] mcycle;
wire [6:0] tstate;
 
assign cen = 1;
 
tv80_core #(Mode, IOWait) i_tv80_core
(
.cen (cen),
.m1_n (m1_n),
.iorq (iorq),
.no_read (no_read),
.write (write),
.rfsh_n (rfsh_n),
.halt_n (halt_n),
.wait_n (wait_n),
.int_n (int_n),
.nmi_n (nmi_n),
.reset_n (reset_n),
.busrq_n (busrq_n),
.busak_n (busak_n),
.clk (clk),
.IntE (),
.stop (),
.A (A),
.dinst (di),
.di (di_reg),
.do (do),
.mc (mcycle),
.ts (tstate),
.intcycle_n (intcycle_n)
);
 
always @*
begin
nxt_mreq_n = 1;
nxt_rd_n = 1;
nxt_iorq_n = 1;
nxt_wr_n = 1;
if (mcycle[0])
begin
if (tstate[1] || tstate[2])
begin
nxt_rd_n = ~ intcycle_n;
nxt_mreq_n = ~ intcycle_n;
nxt_iorq_n = intcycle_n;
end
end // if (mcycle[0])
else
begin
if ((tstate[1] || tstate[2]) && !no_read && !write)
begin
nxt_rd_n = 1'b0;
nxt_iorq_n = ~ iorq;
nxt_mreq_n = iorq;
end
if (T2Write == 0)
begin
if (tstate[2] && write)
begin
nxt_wr_n = 1'b0;
nxt_iorq_n = ~ iorq;
nxt_mreq_n = iorq;
end
end
else
begin
if ((tstate[1] || (tstate[2] && !wait_n)) && write)
begin
nxt_wr_n = 1'b0;
nxt_iorq_n = ~ iorq;
nxt_mreq_n = iorq;
end
end // else: !if(T2write == 0)
end // else: !if(mcycle[0])
end // always @ *
 
always @(negedge clk)
begin
if (!reset_n)
begin
rd_n <= #1 1'b1;
wr_n <= #1 1'b1;
iorq_n <= #1 1'b1;
mreq_n <= #1 1'b1;
end
else
begin
rd_n <= #1 nxt_rd_n;
wr_n <= #1 nxt_wr_n;
iorq_n <= #1 nxt_iorq_n;
mreq_n <= #1 nxt_mreq_n;
end // else: !if(!reset_n)
end // always @ (posedge clk or negedge reset_n)
 
always @(posedge clk)
begin
if (!reset_n)
begin
di_reg <= #1 0;
end
else
begin
if (tstate[2] && wait_n == 1'b1)
di_reg <= #1 di;
end // else: !if(!reset_n)
end // always @ (posedge clk)
endmodule // t80n
 

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