8279 Block Diagram
8279 Block Diagram CPU interface and control section Scan section 8279 Keyboard section Display section 1 .CPU Interface and Control Section Data Buffers The data buffers are 8-bit bi-directional buffers that connect the internal data bus to the external data bus. I/O Control The I/O control section uses the A 0 , CS, RD and WR signals to control data flow to and from the various internal registers and buffers. he data flow to and from the Block Diagram of 8279 is enabled only when CS = 0; otherwise the 8279 signals are in a high impedance state. Control and Timing Registers The control and timing registers store the keyboard and display modes and other operating conditions programmed by the CPU. 2. Scan Section (Scan counter) The scan section has a scan counter which has two modes : Encoded mode decoded mode. Encoded Mode In the encoded mode, the scan counter provides a binary count from 0000 to 1111 on the four scan lines (SC 3 — SC 0 ) with active high outputs....