`ifdef EXECUTE `INSN_RET,`INSN_RETCC: begin case (cycle) 0: `EXEC_READ(`_SP) 1: begin // SPECIAL CASE: cycle does NOT increase linearly with ret! `EXEC_INC_PC // cycle 1 is skipped if we are not retcc case (opcode[4:3]) `INSN_cc_NZ: if (registers[`REG_F][7]) `EXEC_NEWCYCLE `INSN_cc_Z: if (~registers[`REG_F][7]) `EXEC_NEWCYCLE `INSN_cc_NC: if (registers[`REG_F][4]) `EXEC_NEWCYCLE `INSN_cc_C: if (~registers[`REG_F][4]) `EXEC_NEWCYCLE endcase `EXEC_READ(`_SP) // retry the read end 2: `EXEC_READ(`_SP + 1) 3: begin /* twiddle thumbs */ end 4: `EXEC_NEWCYCLE endcase end `endif `ifdef WRITEBACK `INSN_RET,`INSN_RETCC: begin case (cycle) 0: if (opcode[0]) // i.e., not RETCC cycle <= 1; // Skip cycle 1; it gets incremented on the next round. 1: begin /* Nothing need happen here. */ end 2: `_PCL <= rdata; 3: `_PCH <= rdata; 4: begin `_SP <= `_SP + 2; if (opcode[4] && opcode[0]) /* RETI */ ie <= 1; end endcase end `endif