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Arlet 65C02 WIP: Implement BRA

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Change-Id: If732b295d84011212269974b48d3f7a8da6804dc
This commit is contained in:
David Banks
2016-08-01 11:56:01 +01:00
parent aea27b38d7
commit 7418b64cd9
1 changed files with 15 additions and 12 deletions
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27
cpu_65c02.v
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@@ -123,7 +123,7 @@ reg shift; // doing shift/rotate instruction
reg rotate; // doing rotate (no shift)
reg backwards; // backwards branch
reg cond_true; // branch condition is true
reg [2:0] cond_code; // condition code bits from instruction
reg [3:0] cond_code; // condition code bits from instruction
reg shift_right; // Instruction ALU shift/rotate right
reg alu_shift_right; // Current cycle shift right enable
reg [3:0] op; // Main ALU operation for instruction
@@ -882,7 +882,8 @@ always @(posedge clk or posedge reset)
8'b0x00_1000: state <= PUSH0;
8'b0x10_1000: state <= PULL0;
8'b0xx1_1000: state <= REG; // CLC, SEC, CLI, SEI
8'b1xx0_00x0: state <= FETCH; // IMM
8'b11x0_00x0: state <= FETCH; // IMM
8'b1x10_00x0: state <= FETCH; // IMM
8'b1xx0_1100: state <= ABS0; // X/Y abs
8'b1xxx_1000: state <= REG; // DEY, TYA, ...
8'bxxx0_0001: state <= INDX0;
@@ -890,7 +891,8 @@ always @(posedge clk or posedge reset)
8'bxxx0_1001: state <= FETCH; // IMM
8'bxxx0_1101: state <= ABS0; // even E column
8'bxxx0_1110: state <= ABS0; // even E column
8'bxxx1_0000: state <= BRA0; // odd 0 column
8'bxxx1_0000: state <= BRA0; // odd 0 column (Branches)
8'b1000_0000: state <= BRA0; // BRA
8'bxxx1_0001: state <= INDY0; // odd 1 column
8'bxxx1_01xx: state <= ZPX0; // odd 4,5,6,7 columns
8'bxxx1_1001: state <= ABSX0; // odd 9 column
@@ -1207,18 +1209,19 @@ always @(posedge clk )
always @(posedge clk)
if( RDY )
cond_code <= IR[7:5];
cond_code <= IR[7:4];
always @*
case( cond_code )
3'b000: cond_true = ~N;
3'b001: cond_true = N;
3'b010: cond_true = ~V;
3'b011: cond_true = V;
3'b100: cond_true = ~C;
3'b101: cond_true = C;
3'b110: cond_true = ~Z;
3'b111: cond_true = Z;
4'b0001: cond_true = ~N;
4'b0011: cond_true = N;
4'b0101: cond_true = ~V;
4'b0111: cond_true = V;
4'b1001: cond_true = ~C;
4'b1011: cond_true = C;
4'b1101: cond_true = ~Z;
4'b1111: cond_true = Z;
default: cond_true = 1; // BRA is 80
endcase