The document discusses the different modes of the 8255 chip, including Mode 0 for simple input/output, Mode 1 for strobbed input/output where data transfer occurs based on a strobe signal, and Mode 2 for bidirectional strobed mode where data can be input and output using a single strobe. Modes 1 and 2 are described further with Mode 1 separating into input and output modes and Mode 2 referred to as bidirectional mode.

1. 8255 Modes

2. 8255 Modes
• Mode 0: Simple Input/Output Mode
• Mode 1: Strobbed Input/Output Mode
• Mode 2: Strobbed Bidirectional Mode

3. 8255 Mode-1 (Input Mode)

4. 8255 Mode-1 (Input Mode)

5. 8255 Mode-1 (Output Mode)

6. 8255 Mode-1 (Output Mode)

7. 8255 Mode-2 (Bidirectional Mode)

8. 8255 Mode-2 (Bidirectional Mode)