A commercial interface unit uses different names for the handshake lines associated with the transfer of data from the 110 device into the interface unit. The interface input handshake line is labeled STB (strobe), and the interface output handshake line is labeled IBF (input buffer full). A low-level signal on STB loads data from the 110 bus into the interface data register. A high-level signal on IBF indicates that the data item has been accepted by the interface. IBF goes low after an 110 read signal from the CPU when it reads the contents of the data register.

a. Draw a block diagram showing the CPU, the interface, and the 110 device together with the pertinent interconnections among the three units.

b. Draw a timing diagram for the handshaking transfer.

c. Obtain a sequence-of-events flowchart for the transfer from the device to the interface and from the interface to the CPU.