A commercial interface unit uses different names for the handshake lines associated with the transfer of data from the I/O 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 I/O 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 I/O 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 I/O 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.