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    /zipcpu/trunk/rtl
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Rev 3 → Rev 2

/core/memops.v
1,39 → 1,3
///////////////////////////////////////////////////////////////////////////
//
// Filename: memops.v
//
// Project: Zip CPU -- a small, lightweight, RISC CPU soft core
//
// Purpose: A memory unit to support a CPU.
//
// In the interests of code simplicity, this memory operator is
// susceptible to unknown results should a new command be sent to it
// before it completes the last one. Unpredictable results might then
// occurr.
//
// Creator: Dan Gisselquist, Ph.D.
// Gisselquist Tecnology, LLC
//
///////////////////////////////////////////////////////////////////////////
//
// Copyright (C) 2015, Gisselquist Technology, LLC
//
// This program is free software (firmware): 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 (at
// your option) any later version.
//
// This program is distributed in the hope that it will be useful, but WITHOUT
// ANY WARRANTY; without even the implied warranty of MERCHANTIBILITY or
// FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
// for more details.
//
// License: GPL, v3, as defined and found on www.gnu.org,
// http://www.gnu.org/licenses/gpl.html
//
//
///////////////////////////////////////////////////////////////////////////
//
module memops(i_clk, i_rst, i_stb,
i_op, i_addr, i_data, i_oreg,
o_busy, o_valid, o_wreg, o_result,
62,18 → 26,14
if (i_rst)
o_wb_cyc <= 1'b0;
else if (o_wb_cyc)
begin
o_wb_stb <= (o_wb_stb)&&(i_wb_stall);
o_wb_cyc <= (~i_wb_ack);
else if (i_stb) // New memory operation
end else if (i_stb) // New memory operation
begin
// Grab the wishbone
o_wb_cyc <= 1'b1;
always @(posedge i_clk)
if (o_wb_cyc)
o_wb_stb <= (o_wb_stb)&&(i_wb_stall);
else
o_wb_stb <= i_stb; // Grab wishbone on new operation
always @(posedge i_clk)
if (i_stb)
begin
o_wb_stb <= 1'b1;
o_wb_we <= i_op;
o_wb_data <= i_data;
o_wb_addr <= i_addr;
81,13 → 41,13
 
initial o_valid = 1'b0;
always @(posedge i_clk)
o_valid <= (o_wb_cyc)&&(i_wb_ack)&&(~o_wb_we);
o_valid <= (o_wb_cyc)&&(i_wb_ack)&&(~o_wb_we)&&(~i_rst);
assign o_busy = o_wb_cyc;
 
always @(posedge i_clk)
if (i_stb)
if ((i_stb)&&(~o_wb_cyc))
o_wreg <= i_oreg;
always @(posedge i_clk)
if (i_wb_ack)
if ((o_wb_cyc)&&(i_wb_ack))
o_result <= i_wb_data;
endmodule
/core/pipefetch.v
1,18 → 1,10
////////////////////////////////////////////////////////////////////////////////
//
// Filename: pipefetch.v
// Filename: regset.v
//
// Project: Zip CPU -- a small, lightweight, RISC CPU soft core
//
// Purpose: Keeping our CPU fed with instructions, at one per clock and
// with no stalls, can be quite a chore. Worse, the Wishbone
// takes a couple of cycles just to read one instruction from
// the bus. However, if we use pipeline accesses to the Wishbone
// bus, then we can read more and faster. Further, if we cache
// these results so that we have them before we need them, then
// we have a chance of keeping our CPU from stalling. Those are
// the purposes of this instruction fetch module: 1) Pipeline
// wishbone accesses, and 2) an instruction cache.
// Purpose:
//
// Creator: Dan Gisselquist, Ph.D.
// Gisselquist Tecnology, LLC
40,10 → 32,8
module pipefetch(i_clk, i_rst, i_new_pc, i_stall_n, i_pc,
o_i, o_pc, o_v,
o_wb_cyc, o_wb_stb, o_wb_we, o_wb_addr, o_wb_data,
i_wb_ack, i_wb_stall, i_wb_data, i_wb_request);
parameter RESET_ADDRESS=32'h0010_0000,
LGCACHELEN = 6, CACHELEN=(1<<LGCACHELEN),
BUSW=32;
i_wb_ack, i_wb_stall, i_wb_data);
parameter LGCACHELEN = 6, CACHELEN=(1<<LGCACHELEN), BUSW=32;
input i_clk, i_rst, i_new_pc, i_stall_n;
input [(BUSW-1):0] i_pc;
output reg [(BUSW-1):0] o_i;
57,9 → 47,6
//
input i_wb_ack, i_wb_stall;
input [(BUSW-1):0] i_wb_data;
//
// Is the (data) memory unit also requesting access to the bus?
input i_wb_request;
 
// Fixed bus outputs: we read from the bus only, never write.
// Thus the output data is ... irrelevant and don't care. We set it
67,11 → 54,12
assign o_wb_we = 1'b0;
assign o_wb_data = 0;
 
reg [(BUSW-1):0] r_cache_base;
reg [(BUSW-1):0] r_cache_base, r_cache_offset;
reg [(LGCACHELEN):0] r_nvalid, r_acks_waiting;
reg [(BUSW-1):0] cache[0:(CACHELEN-1)];
 
reg [(LGCACHELEN-1):0] r_cache_offset;
wire [(LGCACHELEN-1):0] c_cache_offset;
assign c_cache_offset = r_cache_offset[(LGCACHELEN-1):0];
 
reg r_addr_set;
reg [(BUSW-1):0] r_addr;
79,34 → 67,21
wire [(BUSW-1):0] bus_nvalid;
assign bus_nvalid = { {(BUSW-LGCACHELEN-1){1'b0}}, r_nvalid };
 
// What are some of the conditions for which we need to restart the
// cache?
wire w_pc_out_of_bounds;
assign w_pc_out_of_bounds = ((i_new_pc)&&((r_nvalid == 0)
||(i_pc < r_cache_base)
||(i_pc >= r_cache_base + CACHELEN)));
wire w_ran_off_end_of_cache;
assign w_ran_off_end_of_cache =((r_addr_set)&&((r_addr < r_cache_base)
||(r_addr >= r_cache_base + CACHELEN)));
wire w_running_out_of_cache;
assign w_running_out_of_cache = (r_addr_set)
&&(r_addr >= r_cache_base + (1<<(LGCACHELEN-2))
+ (1<<(LGCACHELEN-1)));
initial r_nvalid = 0;
initial r_cache_base = RESET_ADDRESS;
initial r_cache_base = 0;
always @(posedge i_clk)
begin
if (i_rst)
o_wb_cyc <= 1'b0;
else if ((~o_wb_cyc)&&(i_new_pc)&&(r_nvalid != 0)
&&(i_pc > r_cache_base)
&&(i_pc < r_cache_base + bus_nvalid))
begin
o_wb_cyc <= 1'b0;
// r_cache_base <= RESET_ADDRESS;
// end else if ((~o_wb_cyc)&&(i_new_pc)&&(r_nvalid != 0)
// &&(i_pc >= r_cache_base)
// &&(i_pc < r_cache_base + bus_nvalid))
// begin
// The new instruction is in our cache, do nothing
// with the bus here.
end else if ((o_wb_cyc)&&(w_pc_out_of_bounds))
end else if ((o_wb_cyc)&&(i_new_pc)&&(r_nvalid != 0)
&&((i_pc < r_cache_base)
||(i_pc >= r_cache_base + CACHELEN)))
begin
// We need to abandon our bus action to start over in
// a new region, setting up a new cache. This may
115,33 → 90,36
// interested in that result--whatever it might be.
o_wb_cyc <= 1'b0;
o_wb_stb <= 1'b0;
end else if ((~o_wb_cyc)&&(~r_nvalid[LGCACHELEN])&&(~i_wb_request)&&(r_addr_set))
begin
// Restart a bus cycle that was interrupted when the
// data section wanted access to our bus.
o_wb_cyc <= 1'b1;
o_wb_stb <= 1'b1;
// o_wb_addr <= r_cache_base + bus_nvalid;
end else if ((~o_wb_cyc)&&(
(w_pc_out_of_bounds)||(w_ran_off_end_of_cache)))
((i_new_pc)&&((r_nvalid == 0)
||(i_pc < r_cache_base)
||(i_pc >= r_cache_base + CACHELEN)))
||((r_addr_set)&&((r_addr < r_cache_base)
||(r_addr >= r_cache_base + CACHELEN)))
))
begin
// Start a bus transaction
o_wb_cyc <= 1'b1;
o_wb_stb <= 1'b1;
// o_wb_addr <= (i_new_pc) ? i_pc : r_addr;
// r_nvalid <= 0;
// r_cache_base <= (i_new_pc) ? i_pc : r_addr;
// r_cache_offset <= 0;
end else if ((~o_wb_cyc)&&(w_running_out_of_cache))
o_wb_addr <= (i_new_pc) ? i_pc : r_addr;
r_acks_waiting <= 0;
r_nvalid <= 0;
r_cache_base <= (i_new_pc) ? i_pc : r_addr;
r_cache_offset <= 0;
end else if ((~o_wb_cyc)&&(r_addr_set)
&&(r_addr >= r_cache_base
+ (1<<(LGCACHELEN-2))
+ (1<<(LGCACHELEN-1))))
begin
// If we're using the last quarter of the cache, then
// let's start a bus transaction to extend the cache.
o_wb_cyc <= 1'b1;
o_wb_stb <= 1'b1;
// o_wb_addr <= r_cache_base + (1<<(LGCACHELEN));
// r_nvalid <= r_nvalid - (1<<(LGCACHELEN-2));
// r_cache_base <= r_cache_base + (1<<(LGCACHELEN-2));
// r_cache_offset <= r_cache_offset + (1<<(LGCACHELEN-2));
o_wb_addr <= r_cache_base + (1<<(LGCACHELEN));
r_acks_waiting <= 0;
r_nvalid <= r_nvalid - (1<<(LGCACHELEN-2));
r_cache_base <= r_cache_base + (1<<(LGCACHELEN-2));
r_cache_offset <= r_cache_offset + (1<<(LGCACHELEN-2));
end else if (o_wb_cyc)
begin
// This handles everything ... but the case where
148,15 → 126,21
// while reading we need to extend our cache.
if ((o_wb_stb)&&(~i_wb_stall))
begin
// o_wb_addr <= o_wb_addr + 1;
if ((o_wb_addr - r_cache_base >= CACHELEN-1)
||(i_wb_request))
o_wb_addr <= o_wb_addr + 1;
if (o_wb_addr - r_cache_base >= CACHELEN-1)
o_wb_stb <= 1'b0;
end
 
if ((o_wb_stb)&&(~i_wb_stall)&&(~i_wb_ack))
r_acks_waiting <= r_acks_waiting
+ ((i_wb_ack)? 0:1);
else if ((i_wb_ack)&&((~o_wb_stb)||(i_wb_stall)))
r_acks_waiting <= r_acks_waiting - 1;
 
if (i_wb_ack)
begin
// r_nvalid <= r_nvalid + 1;
cache[r_nvalid[(LGCACHELEN-1):0]+c_cache_offset] <= i_wb_data;
r_nvalid <= r_nvalid + 1;
if ((r_acks_waiting == 1)&&(~o_wb_stb))
o_wb_cyc <= 1'b0;
end
163,50 → 147,6
end
end
 
always @(posedge i_clk)
if ((~o_wb_cyc)&&(
(w_pc_out_of_bounds)||(w_ran_off_end_of_cache)))
r_nvalid <= 0;
else if ((~o_wb_cyc)&&(w_running_out_of_cache))
r_nvalid <= r_nvalid - (1<<(LGCACHELEN-2));
else if ((o_wb_cyc)&&(i_wb_ack))
r_nvalid <= r_nvalid+1;
 
always @(posedge i_clk)
if ((~o_wb_cyc)&&(
(w_pc_out_of_bounds)||(w_ran_off_end_of_cache)))
r_cache_base <= (i_new_pc) ? i_pc : r_addr;
else if ((~o_wb_cyc)&&(w_running_out_of_cache))
r_cache_base <= r_cache_base + (1<<(LGCACHELEN-2));
 
always @(posedge i_clk)
if ((~o_wb_cyc)&&(
(w_pc_out_of_bounds)||(w_ran_off_end_of_cache)))
r_cache_offset <= 0;
else if ((~o_wb_cyc)&&(w_running_out_of_cache))
r_cache_offset <= r_cache_offset + (1<<(LGCACHELEN-2));
 
always @(posedge i_clk)
if ((~o_wb_cyc)&&((w_pc_out_of_bounds)
||(w_ran_off_end_of_cache)))
o_wb_addr <= (i_new_pc) ? i_pc : r_addr;
else if ((o_wb_cyc)&&(o_wb_stb)&&(~i_wb_stall))
o_wb_addr <= o_wb_addr + 1;
 
initial r_acks_waiting = 0;
always @(posedge i_clk)
if (~o_wb_cyc)
r_acks_waiting <= 0;
else if ((o_wb_stb)&&(~i_wb_stall)&&(~i_wb_ack))
r_acks_waiting <= r_acks_waiting + ((i_wb_ack)? 0:1);
else if ((i_wb_ack)&&((~o_wb_stb)||(i_wb_stall)))
r_acks_waiting <= r_acks_waiting - 1;
 
always @(posedge i_clk)
if ((o_wb_cyc)&&(i_wb_ack))
cache[r_nvalid[(LGCACHELEN-1):0]+r_cache_offset]
<= i_wb_data;
 
initial r_addr_set = 1'b0;
always @(posedge i_clk)
if (i_rst)
231,7 → 171,7
 
wire [(LGCACHELEN-1):0] c_rdaddr, c_cache_base;
assign c_cache_base = r_cache_base[(LGCACHELEN-1):0];
assign c_rdaddr = r_addr[(LGCACHELEN-1):0]-c_cache_base+r_cache_offset;
assign c_rdaddr = r_addr[(LGCACHELEN-1):0]-c_cache_base+c_cache_offset;
always @(posedge i_clk)
if (i_stall_n)
o_i <= cache[c_rdaddr];
/core/cpuops.v
57,13 → 57,17
begin
pre_sign <= (i_a[31]);
c <= 1'b0;
casez(i_op)
4'b?000:{c,o_c } <= {(i_b>i_a),i_a - i_b};// CMP/SUB
4'b?001: o_c <= i_a & i_b; // BTST/And
case(i_op)
4'h0: { c, o_c } <= {(i_b>i_a),i_a - i_b};// CMP (SUB)
4'h1: o_c <= i_a & i_b; // BTST (And)
4'h2: o_c <= i_b; // MOV
// 4'h3: o_c <= { i_b[15:0],i_a[15:6],6'h20};//TRAP
// 4'h4: o_c <= i_a[15:0] * i_b[15:0];
4'h5: o_c <= w_rol_result; // ROL
4'h6: o_c <= { i_a[31:16], i_b[15:0] }; // LODILO
4'h7: o_c <= { i_b[15:0], i_a[15:0] }; // LODIHI
4'h8: { c, o_c } <= {(i_b>i_a), i_a - i_b }; // Sub
4'h9: o_c <= i_a & i_b; // And
4'ha: { c, o_c } <= i_a + i_b; // Add
4'hb: o_c <= i_a | i_b; // Or
4'hc: o_c <= i_a ^ i_b; // Xor
/core/zipcpu.v
204,8 → 204,8
wire [31:0] opA_nowait, opB_nowait, opA, opB;
reg opR_wr, opM, opF_wr, op_gie,
opA_rd, opB_rd;
wire [7:0] opFl;
reg [6:0] r_opF;
reg [7:0] opFl;
// reg [6:0] r_opF;
wire [8:0] opF;
wire op_ce;
 
307,12 → 307,10
pf_data,
pf_ack, pf_stall, i_wb_data);
`else // Pipe fetch
pipefetch #(RESET_ADDRESS)
pf(i_clk, i_rst, new_pc, ~dcd_stalled, pf_pc,
pipefetch pf(i_clk, i_rst, new_pc, ~dcd_stalled, pf_pc,
instruction, instruction_pc, pf_valid,
pf_cyc, pf_stb, pf_we, pf_addr, pf_data,
pf_ack, pf_stall, i_wb_data,
mem_cyc);
pf_ack, pf_stall, i_wb_data);
assign instruction_gie = gie;
`endif
 
459,7 → 457,6
// these two bits are redundant. Hence the convoluted expression
// below, arriving at what we finally want in the (now wire net)
// opF.
`define NEWCODE
`ifdef NEWCODE
always @(posedge i_clk)
if (op_ce)
582,7 → 579,7
assign opA = { r_opA[31:8], ((opA_cc[0]) ?
((opA_cc[1])?w_uflags:w_iflags) : r_opA[7:0]) };
assign opB = { r_opB[31:8], ((opB_cc[0]) ?
((opB_cc[1])?w_uflags:w_iflags) : r_opB[7:0]) };
((opA_cc[1])?w_uflags:w_iflags) : r_opB[7:0]) };
 
//
//
/zipsystem.v
82,13 → 82,6
//
///////////////////////////////////////////////////////////////////////////
//
// While I hate adding delays to any bus access, these two are required
// to make timing close in my Basys-3 design.
`define DELAY_EXT_BUS
`define DELAY_DBG_BUS
//
//
// Now, where am I placing all of my peripherals?
`define PERIPHBASE 32'hc0000000
`define INTCTRL 4'h0 //
`define WATCHDOG 4'h1 // Interrupt generates reset signal
155,22 → 148,11
wire dbg_cyc, dbg_stb, dbg_we, dbg_addr, dbg_stall;
wire [31:0] dbg_idata, dbg_odata;
reg dbg_ack;
`ifdef DELAY_DBG_BUS
busdelay #(1,32) wbdelay(i_clk,
i_dbg_cyc, i_dbg_stb, i_dbg_we, i_dbg_addr, i_dbg_data,
o_dbg_ack, o_dbg_stall, o_dbg_data,
dbg_cyc, dbg_stb, dbg_we, dbg_addr, dbg_idata,
dbg_ack, dbg_stall, dbg_odata);
`else
assign dbg_cyc = i_dbg_cyc;
assign dbg_stb = i_dbg_stb;
assign dbg_we = i_dbg_we;
assign dbg_addr = i_dbg_addr;
assign dbg_idata = i_dbg_data;
assign o_dbg_ack = dbg_ack;
assign o_dbg_stall = dbg_stall;
assign o_dbg_data = dbg_odata;
`endif
 
//
//
496,22 → 478,11
ext_addr, ext_odata, ext_we, ext_stb,
ext_cyc, ext_ack, ext_stall);
 
`ifdef DELAY_EXT_BUS
busdelay #(32,32) extbus(i_clk,
ext_cyc, ext_stb, ext_we, ext_addr, ext_odata,
ext_ack, ext_stall, ext_idata,
o_wb_cyc, o_wb_stb, o_wb_we, o_wb_addr, o_wb_data,
i_wb_ack, i_wb_stall, i_wb_data);
`else
assign o_wb_cyc = ext_cyc;
assign o_wb_stb = ext_stb;
assign o_wb_we = ext_we;
assign o_wb_addr = ext_addr;
assign o_wb_data = ext_odata;
assign ext_ack = i_wb_ack;
assign ext_stall = i_wb_stall;
assign ext_idata = i_wb_data;
`endif
 
wire tmr_ack;
assign tmr_ack = (tma_ack|tmb_ack|tmc_ack|jif_ack);

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