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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.
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:
relocation
DQ: Define Quad word:- This directive is taken in use to direct the assembler to reserve 4 words (8 bytes) of memory for the specified variable and can initialise it having
Instruction Formats A machine language instruction format has 1 or more number of fields linked with it. The first field is known as operation code field or op code field, whic
SBB: Subtract with Borrow :- The subtract with borrow instruction subtracts the source operand and the borrow flag (CF) which might reflect the result of the past calculations,
to separate positive and negative numbers
Write a program that allows a user to encrypt/decrypt a message using a shift cipher. The user should specify the key and the message. Your program should be able to handle messa
$NOMOD51 $NOSYMBOLS ;***************************************************************************** ; Spring 2013 Project ; ; FILE NAME : Project.ASM ; DATE : 3/30/20
Can any one assist me with this program. I am not efficient with assembly language and I need assistance badly. I am not asking anyone to do my work I just need help step by step
LIST p=18f4550 #include org 0x0000 movlw 0x00 _________ movlw 0xFF movwf PORTB end .
END : END of Program:- The END directive marks the ending of the assembly language program. When the assembler comes across this END directive, it avoided the source lines avai
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