Pin Diagram of 8257

Pin Diagram of 8257: Fig. 14.61 shows Pin Diagram of 8257. Data Bus (D0-D7) : These are bi-directional tri-state signals connected to the system data bus. When CPU is having control of system bus it can access contents of address register, status register, mode set register, and a terminal count register and it can also […]

Features of 8257 DMA Controller

Features of 8257 DMA Controller: The Features of 8257 DMA Controller are follows, 1. It is a programmable; 4-channel, direct memory access controller. Each channel can be programmed individually. Therefore, we can interface 4 input/output devices with 8257. 2. Each channel includes a 16-bit DMA address register and a 14-bit counter. DMA address register gives the […]

Programmable DMA Controller 8257

Programmable DMA Controller 8257: In microprocessor based systems data transfer can be controlled by either software or hardware. Upto this point we have used program instructions to transfer data from I/O device to memory or from memory to I/O device. To transfer data by Programmable DMA Controller 8257 method microprocessor has to do following tasks […]

Interfacing 8251 with 8085

Interfacing 8251 with 8085: Fig. 14.44 shows the Interfacing 8251 with 8085 in I/O mapped I/O technique. Here, RD and WR signals are activated by CPU when IO/M signal is high, indicating I/O bus cycle. The address line A0 is connected to the C/D input .of the 8251A. The RESET and CLK signals are driven […]

Types of Data Communication of 8251

Types of Data Communication of 8251: We know that, 8251A is Universal Synchronous, Asynchronous, Receiver, and Transmitter. Therefore Types of Data Communication of 8251 can take place with four different ways. Asynchronous transmission Asynchronous reception Synchronous transmission Synchronous reception These communication modes can be enabled by writing proper mode and command instructions. The mode instruction […]

Block Diagram of 8251 Microcontroller

Block Diagram of 8251 Microcontroller: Fig. 14.37 shows the block diagram of IC Block Diagram of 8251 Microcontroller. It includes : Data bus buffer, Read/Write control logic, modem control, Transmit buffer, Transmit Control, Receiver Buffer and Receiver control. Data Bus Buffer : This tri-state, bi-directional, 8-bit buffer is used to interface Block Diagram of 8251 […]