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microaddr_counter.v
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microaddr_counter.v
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import microaddr_types::uaddr_t;
module microaddr_counter(
input bit clk,
input bit reset,
input bit zflag,
input byte unsigned M,
input microaddr_types::cmd_t cmd,
input uaddr_t load_addr,
output uaddr_t addr
);
parameter opjump_table_file = "";
uaddr_t next_addr;
uaddr_t call_stack[4];
uaddr_t next_call_stack[4];
bit[1:0] call_stack_ptr;
bit[1:0] next_call_stack_ptr;
uaddr_t opjump_table[256];
initial begin
$readmemh(opjump_table_file, opjump_table);
end //intial
// define command functionality
always_comb begin
next_call_stack_ptr = call_stack_ptr;
next_call_stack = call_stack;
unique case(cmd)
microaddr_types::NONE:
next_addr = addr;
microaddr_types::INC:
next_addr = addr + 1;
microaddr_types::JMP:
next_addr = load_addr;
microaddr_types::JNZ:
next_addr = zflag == 0 ? load_addr : addr + 1;
microaddr_types::CALL: begin
next_call_stack[call_stack_ptr] = addr + 1;
next_call_stack_ptr = call_stack_ptr + 1;
next_addr = load_addr;
end
microaddr_types::RET: begin
next_addr = call_stack[call_stack_ptr - 1];
next_call_stack_ptr = call_stack_ptr - 1;
end
microaddr_types::OPJMP:
next_addr = opjump_table[M]
default:
next_addr = 0;
endcase //cmd
if(reset == 1) begin
next_addr = 0;
next_call_stack_ptr = 0;
end
end // always_comb
always_ff @(posedge clk) begin
addr <= next_addr;
call_stack_ptr <= next_call_stack_ptr;
call_stack <= next_call_stack;
end //always_ff
endmodule //microaddr_counter