Abstract: A one-chip microcomputer system of the present invention, includes: a display driving circuit for driving a display device, a scanning circuit for outputting a key scanning signal to scan a keyboard switch; a common pert used for scanning the keyboard switch, and driving the display device; and a controller for controlling parallel processing of scanning the keyboard switch and driving the display device.

Abstract: A terminal printer can simultaneously receive print data from a plurality of host devices. The terminal printer has one reception buffer memory to which reception buffers are allocated on the basis of number information of the connected host devices, and a buffer management memory which manages the reception buffer memory. The buffer management memory is configured by region which respectively store terminal addresses of the host devices using the reception buffers, and regions which respectively store serial numbers of lastly received packets in correspondence with the reception buffers. When a packet is received, the terminal address of the host device included in the packet is compared with the terminal addresses stored in the buffer management memory. Subsequently, the packet is stored into the reception buffer of the reception buffer memory which is designated by the coincident terminal address.

Abstract: A data error-checking system including a transmitting cash register and a receiving cash register, connected to each other in series in a loop formation. Its operation includes the serial transfer of data from the transmitting cash register to the receiving cash register simultaneous with data transfer from the receiving cash register to the transmitting cash register, and comparison of the data transferred from the transmitting cash register with the corresponding data transferred back from the receiving cash register to the transmitting cash register.

Abstract: A printer mounted on an electronic cash register (ECR) performs printing on printing paper by moving a print head left to right and right to left, i.e. bidirectionally. The printer uses right and left reset signals to determine the print start position and printing direction of the print head, the right and left reset signals being fed alternately and regularly to the driving circuit for the print head for performing bidirectional printing, thereby assuring correct bidirectional printing. The right and left reset signals are constantly monitored. If the reset signals of the same kinds are successively detected, it is judged that trouble has occurred, hampering correct bidirectional printing, and notice is issued accordingly.