DATA AUTOMATIC READING SYSTEM AND AUTOMATIC WRITING SYSTEM

摘要

PURPOSE:To reduce the burden of a CPU by latching the start address and the data size outputted from the CPU and automatically adding a prescribed value to the start address to generate an update address and stopping the update at the time when the number of times of update coincides with the data size. CONSTITUTION:A start address (n) and a data size are sent from the CPU and are latched in latch circuits 13 and 14 respectively. The upper address of the start address latched in the latch circuit 13 is inputted to a font ROM 10, and the lower address is inputted to terminals A1 to A4 of the font ROM 10 through a counter 15. Font data is successively read out from the font ROM 10 with the start address designated by the CPU as the start point, and this read operation is terminated when the data volume corresponding to the data size is completely read out. It is sufficient for the CPU to output only a trigger ACK signal, the start address, and the data size in this operation, and thereafter, the read operation is automatically executed. Thus, the burden of the CPU is reduced.