8051 microcontrollers

QUESTIONS AND PROBLEMS 8.1 What is the basic difference between main memory and secondary memory? 8.2 Compare the basic features of hard disk, floppy disk and Zip disk. 8.3 What are the main differences between CD and DVD memories? 8.4 Name the methods used in main memory array design. What are the advantages and disadvantages of each. 8.5 The block diagram of a 512 x 8 RAM chip is shown in Figure P8.5. In this arrangement, the memory chip is enabled only when CS 1 = L and CS2 = H. Design a 1 K x 8 RAM system using this chip as the building block. Draw a neat logic diagram of your implementation. Assume that the microprocessor can directly address 64K with a RIW and 8 data pins. Using linear decoding and don't­ care conditions as 1's, determine the memory map in hex. 8.6 Consider the hardware schematic shown in Figure P8.6. (a) Determine the address map of this system. Note: M EM R=O for read, MEMR=l for write and, M/10=0 for I/O and MI/O=l for memory. (...

8.4.2 Pipeline Processing The purpose of this section is to provide a brief overview of pipelining. Basic Concepts Assume a task T is carried out by performing four activities: AI, A2, A3, and A4, in that order. Hardware Hi is designed to perform the activity Ai. Hi is referred to as a segment, and it essentially contains combinational circuit elements. Consider the arrangement shown in Figure 8.45. In this configuration, a latch is placed between two segments so the result computed by one segment can serve as input to the following segment during the next clock period. The execution of four tasks Tl, T2, T3, and T4 using the hardware of Figure 8.45 is described using a space-time chart shown in Figure 8.46. Initially, task Tl is handled by segment I. After the first clock, segment 2 is busy with Tl while segment 1 is busy with T2. Continuing in this manner, the task Tl is completed at the end of the fourth clock. However, following this point, one task is shipped out per...

8.2.3 Direct Memory Access (DMA) Direct memory access (DMA) is a technique that transfers data between a microcomputer's memory and an I/O device without involving the microprocessor. DMA is widely used in transferring large blocks of data between a peripheral device such as a hard disk and the microcomputer's memory. The DMA technique uses a DMA controller chip for the data­ transfer operations. The DMA controller chip implements various components such as a counter containing the length of data to be transferred in hardware in order to speed up data transfer. The main functions of a typical DMA controller are summarized as follows: The I/O devices request DMA operation via the DMA request line of the controller chip. The controller chip activates the microprocessor HOLD pin, requesting the microprocessor to release the bus. The processor sends HLDA (hold acknowledge) back to the DMA controller, indicating that the bus is disabled. The DMA controller pl...

8.2 Input/Output One communicates with a microcomputer system via the I/O devices interfaced to it. The user can enter programs and data using the keyboard on a terminal and execute the programs to obtain results. Therefore, the I/O devices connected to a microcomputer system provide an efficient means of communication between the microcomputer and the outside world. These I/O devices are commonly called "peripherals" and include keyboards, CRT displays, printers, and disks. The characteristics of the I/O devices are normally different from those of the microcomputer. For example, the speed of operation of the peripherals is usually slower than that of the microcomputer, and the word length of the microcomputer may be different from the data format of the peripheral devices. To make the characteristics of the I/O devices compatible with those of the microcomputer, interface hardware circuitry between the microcomputer and I/O devices is necessary. Interfaces provide all i...