<Li> Mode 0 - Simple I / O </Li> <Li> Mode 1 - Strobed I / O </Li> <Li> Mode 2 - Strobed Bi-directional I / O </Li> <Ul> <Li> D, D, D, D are assigned for port C lower, port B, port C upper and port A respectively . When these bits are 1, the corresponding port acts as an input port . For e.g., if D = D = 1, then lower port C and port A act as input ports . If these bits are 0, then the corresponding port acts as an output port . For e.g., if D = D = 0, then port B and upper port C act as output ports . </Li> <Li> D is used for mode selection of Group B (port B and lower port C). When D = 0, mode 0 is selected and when D = 1, mode 1 is selected . </Li> <Li> D & D are used for mode selection of Group A (port A and upper port C). The selection is done as follows: </Li> </Ul>

Draw the bit pattern of control word for 8255