ORDER STORAGE CONTROL CIRCUIT

摘要

PURPOSE:To always secure a state where the order storage is fixed by providing a circuit which detects that the order stored in an order storage control circuit is unfixed. CONSTITUTION:A latest area detecting circuit 5 consists of 3-input NAND circuits B1-B4; while an oldest area detecting circuit 6 consists of 3-input NAND circuits B5-B8. Then an area unfixed state detecting circuit 7 consists of NAND circuits B9-B11. An oldest area setting circuit 8 which sets forcibly the oldest area in a state where the oldest or latest state does not exist consists of NOR circuits C1-C3, an inverter A7 and a NAND circuit B12. An order replacement circuit 9 which rewrites forcibly a 6-bit memory circuit storing the order storage of areas in a state where the oldest or latest area does not exist consists of an AND circuit D1 which inputs a write signal phiwe and the output of the circuit 7 and an inverter A8.