Epson TF-20 Reference Manual page 34

5. HARDWARE
The TF-20 is an intelligent flexible disk unit incorporating a CPU, a 64K-byte
memory and l/0's. Therefore, it lightens the workload for file management
of the CPU in the host computer and reduces the amount of memory
space in the host computer to be occupied by the operating system (OS).
The TF-20 features the following:
(1) Incorporates a high-speed serial interface for connection with the
HX-20.
(2) Performs all file management by transferring necessary information to
and from the HX-20.
5.1 Hardware Configuration