TK2633: MICROPROCESSOR & INTERFACING Programming Techniques Dr. Masri Ayob: TK2633

LOOPING The programming technique used to instruct the MPU to repeat task. Continuous loop Conditional loop Repeat task until certain conditions are met. Some loop include indexing along with counter. Indexing: pointing or referencing objects with sequential numbers, i.e. data in memory are accessed by referencing to their memory locations. Dr. Masri Ayob: TK2633

COUNTER Counter. Counter is constructed by loading a number to any register. Then use INR or DCR to increment or decrement the number respectively. Loop is used to update counter value and every iteration the number is inspected to check whether the number is at maximum or minimum. Dr. Masri Ayob: TK2633 Rajah 1

BLOCK DATA TRANSFERS In many systems, blocks of information are transferred from one place to another in the microprocessor’s memory. Transferring Blocks of Bytes. Transferring Blocks of Words. Dr. Masri Ayob: TK2633 Rajah 1

BLOCK DATA TRANSFERS Suppose that a block of 10 bytes of data, beginning at memory location 2080H, is transferred to a block of memory beginning at location 2090H. The simplest method, is to use the LDA and STA instruction to transfer each byte. Long program A more efficient way to transfer a block of data uses the programmed-loop and counter. Dr. Masri Ayob: TK2633 Rajah 1

Flowchart Flowchart required to transfer a block of bytes from one area of memory to another . Dr. Masri Ayob: TK2633

Transfer 10 bytes of data Dr. Masri Ayob: TK2633

BLOCK DATA TRANSFERS The program uses: the HL register pair to indirectly address the source block of data. The DE register pair to indirectly address the destination block. Transfers use the MOV A,M instruction to load the accumulator from a source block memory location. Next, the STAX D instruction stores the accumulator data into a destination block memory location. The B register functions as a counter in this example. Dr. Masri Ayob: TK2633 Rajah 1

BLOCK DATA TRANSFERS Large- byte block transfer >256 (FF) bytes? Program requires a register pair as the counter. Example: A block of bytes beginning at location 01OOH is transferred to a block beginning at location 2800H. The length of this block is 300 (12CH) bytes. Dr. Masri Ayob: TK2633

BLOCK DATA TRANSFERS Dr. Masri Ayob: TK2633

Transferring Blocks of Words In certain applications, 16-bit words of data must be transferred. Dr. Masri Ayob: TK2633

Transferring Blocks of Words Main Program Dr. Masri Ayob: TK2633

Transferring Blocks of Words Dr. Masri Ayob: TK2633

BLOCK EXCHANGES Block exchanges are similar to block transfers except that the data are taken from one block of memory and exchanged with the data in a second block of memory. Their main application is in sorting character strings and numeric data. Dr. Masri Ayob: TK2633

Byte Block Exchanges Suppose that we must exchange the 80H bytes of memory beginning at location 2800H with the 80H bytes of memory beginning at location 2880H. Dr. Masri Ayob: TK2633

Byte Block Exchanges Dr. Masri Ayob: TK2633

Word Block Exchanges: Exercise Suppose that we must exchange the 500H words of memory beginning at location 9000H with the 500H words of memory beginning at location 9100H. Dr. Masri Ayob: TK2633

Thank you Q&A Dr. Masri Ayob: TK2633