JPS6155709B

PURPOSE:To keep stored data in a fixed state without allowing them to change until sending a seris of data has been completed by making a slave machine wait putting it in a machine lock state. CONSTITUTION:In a slave machine S1, a Central Processing Unit (CPU) 4 receives a request for data transfer from a master machine M and transfers in parts information of memory capacity and sales data. A random access memory (RAM) 15 in the salve machine S1 stores the sales data under the control of the CPU 4. A means of memory 16 is counted down in every split transfer to the master machine M by the control of the CPU 4. A means of decision 17 decides the contents of the means of memory 16 and inputs a machine lock signal or a machine lock release signal to the CPU 4. On the other and, the CPU 4 receives a signal requesting a slip from the master machine M, and if a transfer sequence does not agree, prints the same error message by a means of printing 19 and at the same time, releases the machine lock state.