8251 programmable/communication interface-microprocessor, Assembly Language

8251 Programmable/Communication Interface

As an instance of a serial interface device let us suppose Intel's 8251 A programmable communication interfaces. The 8251A is diagrammed in given figure. It is capable of being programmed for synchronous / asynchronous communication.  The data that is in buffer and data-out buffer registers share the similar port address. For input, the serial bit stream is arriving on the R x D pin is shifted into the receiver shift register and then the data bits are transferred to the data-in buffer register, where they might be input by the CPU. On the other hand on output the data bits put in the data-out buffer register by the CPU are transferred to the transmitter shift register and, along with the essential synchronization bits, are shifted out through the T x D pin. Among other things the contents of the mode register, which are begin by the executing program, determine whether the 8251A is in synchronous mode or asynchronous mode and the format of the characters being received and transmitted. The control register, which is set by the program, controls the operation of the interface, and the status register makes sure information available to the executing program. Obviously, the sync character registers are for storing the sync characters required for synchronous communication.

1142_8251.jpg

Even though all 7 of the registers on the left side of Figure 4.7 may be accessed by the processor, the 8251A is associated with only 2 port addresses. The C/D pin is linked to the address line AO and AO differentiates the 2 port addresses. The 8251A internally interprets the C/D, RD, and WR signals as follows:

1611_8251 signals.jpg

Posted Date: 10/10/2012 7:45:42 AM | Location : United States







Related Discussions:- 8251 programmable/communication interface-microprocessor, Assignment Help, Ask Question on 8251 programmable/communication interface-microprocessor, Get Answer, Expert's Help, 8251 programmable/communication interface-microprocessor Discussions

Write discussion on 8251 programmable/communication interface-microprocessor
Your posts are moderated
Related Questions
The addressing modes for the sequential control transfer instructions are described below:   1. Immediate: Immediate data is a part of instruction,in this type of addressin

Compute the Fibonacci sequence - assembly program: Problem: Fibonacci   In this problem you will write a program that will compute the first 20 numbers in the Fibonacci sequ

I/O interface I/O  devices such as displays and keyboards  establish  communication of computer with outside world. Devices may be interfaced in 2 ways Memory mapped I/O and I/

Prime Finder - assembly program: Problem:  Prime Finder   In this problem you will write a small program that tests whether a given integer is a prime number or not.  Let's

Internal Architecture of Microprocessor : The architecture of 8086 provides a number of improvements over 8085 architecture. It supports a, a set of 16-bit registers ,16-bit AL

A/D conversion: Basic tasks: (a) Write a program that will read and display the analog voltage on pin PE7 approximately once every second. (b) Write a program that will read and d

to separate positive and negative numbers

The definitions of the bits in ICWI are following: Always set to the value 1. It directs the received byte to ICWI as oppose to OCW2 or OCW3. Which also utilize the even addr

Please let me know if you can do an assignment in the next 12 hours

move a byte string ,16 bytes long from the offset 0200H to 0300H in the segment 7000H..