Abstract: A controller implemented on a single LSI MOS chip is described for linking a typewriter console to a processor unit. The controller comprises a FIFO (First-In-First-Out) buffer for storing the keyboard data characters read-out from the console. The buffer includes a flag for each stage, each flag being controlled to assume a first condition when its respective stage is occupied by a character, and a second condition when it is vacant of a character. The keyboard data characters are inputted into the first stage by strobe pulses, and are continuously shifted by high-speed clock pulses to the highest stage of the buffer whose flag is in the stage-vacant condition, the characters being read-out from the last stage. The buffer includes means for preventing the entry of a new character, and also for providing an indication of an "Overflow" condition, whenever a strobe pulse is received by the buffer while the first-stage flag of the buffer is in the stage-occupied condition.