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Add WAI instruction

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This commit is contained in:
Byron Lathi
2026-04-18 16:02:36 -07:00
parent ef2cc5ab45
commit 8f19e45b40
1 changed files with 14 additions and 2 deletions
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16
cpu_65c02.v
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@@ -48,7 +48,7 @@
// `define IMPLEMENT_CORRECT_BCD_FLAGS
module cpu_65c02( clk, reset, AB, DI, DO, WE, IRQ, NMI, RDY, SYNC );
module cpu_65c02( clk, reset, AB, DI, DO, WE, IRQ, NMI, RDY, RDY_O, SYNC );
input clk; // CPU clock
input reset; // reset signal
@@ -59,6 +59,7 @@ output WE; // write enable
input IRQ; // interrupt request
input NMI; // non-maskable interrupt request
input RDY; // Ready signal. Pauses CPU when RDY=0
output reg RDY_O; // Ready output signal. Low during WAI, high otherwise
output reg SYNC; // AB is first cycle of the intruction
/*
@@ -261,7 +262,8 @@ parameter
IND0 = 6'd50, // (ZP) - fetch ZP address, and send to ALU (+0)
JMPIX0 = 6'd51, // JMP (,X)- fetch LSB and send to ALU (+X)
JMPIX1 = 6'd52, // JMP (,X)- fetch MSB and send to ALU (+Carry)
JMPIX2 = 6'd53; // JMP (,X)- Wait for ALU (only if needed)
JMPIX2 = 6'd53, // JMP (,X)- Wait for ALU (only if needed)
WAI = 6'd54; // WAI - Wait for interrupt, then go to decode
`ifdef SIM
@@ -326,6 +328,7 @@ always @*
JMPIX0: statename = "JMPIX0";
JMPIX1: statename = "JMPIX1";
JMPIX2: statename = "JMPIX2";
WAI: statename = "WAI";
endcase
@@ -806,6 +809,12 @@ always @*
default: CI = 0;
endcase
always @*
if (state == WAI)
RDY_O = 1'b0;
else
RDY_O = 1'b1;
/*
* Processor Status Register update
*
@@ -956,6 +965,7 @@ always @(posedge clk or posedge reset)
8'b0110_0000: state <= RTS0;
8'b0110_1100: state <= JMPI0;
8'b0111_1100: state <= JMPIX0;
8'b1100_1011: state <= WAI;
`ifdef IMPLEMENT_NOPS
8'bxxxx_xx11: state <= REG; // (NOP1: 3/7/B/F column)
8'bxxx0_0010: state <= FETCH; // (NOP2: 2 column, 4 column handled correctly below)
@@ -1061,6 +1071,8 @@ always @(posedge clk or posedge reset)
BRK2 : state <= BRK3;
BRK3 : state <= JMP0;
WAI : state <= ( (~I & IRQ) | NMI_edge ) ? DECODE : WAI;
endcase