1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
|
//----------------------------------------------------------------------------
// Copyright (C) 2009 , Olivier Girard
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in the
// documentation and/or other materials provided with the distribution.
// * Neither the name of the authors nor the names of its contributors
// may be used to endorse or promote products derived from this software
// without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
// OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
// THE POSSIBILITY OF SUCH DAMAGE
//
//----------------------------------------------------------------------------
//
// *File Name: omsp_alu.v
//
// *Module Description:
// openMSP430 ALU
//
// *Author(s):
// - Olivier Girard, olgirard@gmail.com
//
//----------------------------------------------------------------------------
// $Rev: 134 $
// $LastChangedBy: olivier.girard $
// $LastChangedDate: 2012-03-22 21:31:06 +0100 (Thu, 22 Mar 2012) $
//----------------------------------------------------------------------------
`ifdef OMSP_NO_INCLUDE
`else
`include "openMSP430_defines.v"
`endif
module omsp_alu (
// OUTPUTs
alu_out, // ALU output value
alu_out_add, // ALU adder output value
alu_stat, // ALU Status {V,N,Z,C}
alu_stat_wr, // ALU Status write {V,N,Z,C}
// INPUTs
dbg_halt_st, // Halt/Run status from CPU
exec_cycle, // Instruction execution cycle
inst_alu, // ALU control signals
inst_bw, // Decoded Inst: byte width
inst_jmp, // Decoded Inst: Conditional jump
inst_so, // Single-operand arithmetic
op_dst, // Destination operand
op_src, // Source operand
status // R2 Status {V,N,Z,C}
);
// OUTPUTs
//=========
output [15:0] alu_out; // ALU output value
output [15:0] alu_out_add; // ALU adder output value
output [3:0] alu_stat; // ALU Status {V,N,Z,C}
output [3:0] alu_stat_wr; // ALU Status write {V,N,Z,C}
// INPUTs
//=========
input dbg_halt_st; // Halt/Run status from CPU
input exec_cycle; // Instruction execution cycle
input [11:0] inst_alu; // ALU control signals
input inst_bw; // Decoded Inst: byte width
input [7:0] inst_jmp; // Decoded Inst: Conditional jump
input [7:0] inst_so; // Single-operand arithmetic
input [15:0] op_dst; // Destination operand
input [15:0] op_src; // Source operand
input [3:0] status; // R2 Status {V,N,Z,C}
//=============================================================================
// 1) FUNCTIONS
//=============================================================================
function [4:0] bcd_add;
input [3:0] X;
input [3:0] Y;
input C_;
reg [4:0] Z_;
begin
Z_ = {1'b0,X}+{1'b0,Y}+{4'b0,C_};
if (Z_<5'd10) bcd_add = Z_;
else bcd_add = Z_+5'd6;
end
endfunction
//=============================================================================
// 2) INSTRUCTION FETCH/DECODE CONTROL STATE MACHINE
//=============================================================================
// SINGLE-OPERAND ARITHMETIC:
//-----------------------------------------------------------------------------
// Mnemonic S-Reg, Operation Status bits
// D-Reg, V N Z C
//
// RRC dst C->MSB->...LSB->C * * * *
// RRA dst MSB->MSB->...LSB->C 0 * * *
// SWPB dst Swap bytes - - - -
// SXT dst Bit7->Bit8...Bit15 0 * * *
// PUSH src SP-2->SP, src->@SP - - - -
// CALL dst SP-2->SP, PC+2->@SP, dst->PC - - - -
// RETI TOS->SR, SP+2->SP, TOS->PC, SP+2->SP * * * *
//
//-----------------------------------------------------------------------------
// TWO-OPERAND ARITHMETIC:
//-----------------------------------------------------------------------------
// Mnemonic S-Reg, Operation Status bits
// D-Reg, V N Z C
//
// MOV src,dst src -> dst - - - -
// ADD src,dst src + dst -> dst * * * *
// ADDC src,dst src + dst + C -> dst * * * *
// SUB src,dst dst + ~src + 1 -> dst * * * *
// SUBC src,dst dst + ~src + C -> dst * * * *
// CMP src,dst dst + ~src + 1 * * * *
// DADD src,dst src + dst + C -> dst (decimaly) * * * *
// BIT src,dst src & dst 0 * * *
// BIC src,dst ~src & dst -> dst - - - -
// BIS src,dst src | dst -> dst - - - -
// XOR src,dst src ^ dst -> dst * * * *
// AND src,dst src & dst -> dst 0 * * *
//
//-----------------------------------------------------------------------------
// * the status bit is affected
// - the status bit is not affected
// 0 the status bit is cleared
// 1 the status bit is set
//-----------------------------------------------------------------------------
// Invert source for substract and compare instructions.
wire op_src_inv_cmd = exec_cycle & (inst_alu[`ALU_SRC_INV]);
wire [15:0] op_src_inv = {16{op_src_inv_cmd}} ^ op_src;
// Mask the bit 8 for the Byte instructions for correct flags generation
wire op_bit8_msk = ~exec_cycle | ~inst_bw;
wire [16:0] op_src_in = {1'b0, {op_src_inv[15:8] & {8{op_bit8_msk}}}, op_src_inv[7:0]};
wire [16:0] op_dst_in = {1'b0, {op_dst[15:8] & {8{op_bit8_msk}}}, op_dst[7:0]};
// Clear the source operand (= jump offset) for conditional jumps
wire jmp_not_taken = (inst_jmp[`JL] & ~(status[3]^status[2])) |
(inst_jmp[`JGE] & (status[3]^status[2])) |
(inst_jmp[`JN] & ~status[2]) |
(inst_jmp[`JC] & ~status[0]) |
(inst_jmp[`JNC] & status[0]) |
(inst_jmp[`JEQ] & ~status[1]) |
(inst_jmp[`JNE] & status[1]);
wire [16:0] op_src_in_jmp = op_src_in & {17{~jmp_not_taken}};
// Adder / AND / OR / XOR
wire [16:0] alu_add = op_src_in_jmp + op_dst_in;
wire [16:0] alu_and = op_src_in & op_dst_in;
wire [16:0] alu_or = op_src_in | op_dst_in;
wire [16:0] alu_xor = op_src_in ^ op_dst_in;
// Incrementer
wire alu_inc = exec_cycle & ((inst_alu[`ALU_INC_C] & status[0]) |
inst_alu[`ALU_INC]);
wire [16:0] alu_add_inc = alu_add + {16'h0000, alu_inc};
// Decimal adder (DADD)
wire [4:0] alu_dadd0 = bcd_add(op_src_in[3:0], op_dst_in[3:0], status[0]);
wire [4:0] alu_dadd1 = bcd_add(op_src_in[7:4], op_dst_in[7:4], alu_dadd0[4]);
wire [4:0] alu_dadd2 = bcd_add(op_src_in[11:8], op_dst_in[11:8], alu_dadd1[4]);
wire [4:0] alu_dadd3 = bcd_add(op_src_in[15:12], op_dst_in[15:12],alu_dadd2[4]);
wire [16:0] alu_dadd = {alu_dadd3, alu_dadd2[3:0], alu_dadd1[3:0], alu_dadd0[3:0]};
// Shifter for rotate instructions (RRC & RRA)
wire alu_shift_msb = inst_so[`RRC] ? status[0] :
inst_bw ? op_src[7] : op_src[15];
wire alu_shift_7 = inst_bw ? alu_shift_msb : op_src[8];
wire [16:0] alu_shift = {1'b0, alu_shift_msb, op_src[15:9], alu_shift_7, op_src[7:1]};
// Swap bytes / Extend Sign
wire [16:0] alu_swpb = {1'b0, op_src[7:0],op_src[15:8]};
wire [16:0] alu_sxt = {1'b0, {8{op_src[7]}},op_src[7:0]};
// Combine short paths toghether to simplify final ALU mux
wire alu_short_thro = ~(inst_alu[`ALU_AND] |
inst_alu[`ALU_OR] |
inst_alu[`ALU_XOR] |
inst_alu[`ALU_SHIFT] |
inst_so[`SWPB] |
inst_so[`SXT]);
wire [16:0] alu_short = ({17{inst_alu[`ALU_AND]}} & alu_and) |
({17{inst_alu[`ALU_OR]}} & alu_or) |
({17{inst_alu[`ALU_XOR]}} & alu_xor) |
({17{inst_alu[`ALU_SHIFT]}} & alu_shift) |
({17{inst_so[`SWPB]}} & alu_swpb) |
({17{inst_so[`SXT]}} & alu_sxt) |
({17{alu_short_thro}} & op_src_in);
// ALU output mux
wire [16:0] alu_out_nxt = (inst_so[`IRQ] | dbg_halt_st |
inst_alu[`ALU_ADD]) ? alu_add_inc :
inst_alu[`ALU_DADD] ? alu_dadd : alu_short;
assign alu_out = alu_out_nxt[15:0];
assign alu_out_add = alu_add[15:0];
//-----------------------------------------------------------------------------
// STATUS FLAG GENERATION
//-----------------------------------------------------------------------------
wire V_xor = inst_bw ? (op_src_in[7] & op_dst_in[7]) :
(op_src_in[15] & op_dst_in[15]);
wire V = inst_bw ? ((~op_src_in[7] & ~op_dst_in[7] & alu_out[7]) |
( op_src_in[7] & op_dst_in[7] & ~alu_out[7])) :
((~op_src_in[15] & ~op_dst_in[15] & alu_out[15]) |
( op_src_in[15] & op_dst_in[15] & ~alu_out[15]));
wire N = inst_bw ? alu_out[7] : alu_out[15];
wire Z = inst_bw ? (alu_out[7:0]==0) : (alu_out==0);
wire C = inst_bw ? alu_out[8] : alu_out_nxt[16];
assign alu_stat = inst_alu[`ALU_SHIFT] ? {1'b0, N,Z,op_src_in[0]} :
inst_alu[`ALU_STAT_7] ? {1'b0, N,Z,~Z} :
inst_alu[`ALU_XOR] ? {V_xor,N,Z,~Z} : {V,N,Z,C};
assign alu_stat_wr = (inst_alu[`ALU_STAT_F] & exec_cycle) ? 4'b1111 : 4'b0000;
endmodule // omsp_alu
`ifdef OMSP_NO_INCLUDE
`else
`include "openMSP430_undefines.v"
`endif
|
