Letter Tube Preparation Knowledge point explaining • Input and output of the computer hardware base

The Information System Management Engineer is an intermediate examination in the National computer Technology and software Professional Technical Qualification Examination (hereinafter referred to as the Software Qualification examination). The examination of Information System Management engineer requires examinee to master the relevant knowledge content of computer system, operating system, database, computer network, informationization and information system. The Information System Management Engineer Exam requires a wide range of content, and what are the key points to be mastered during preparation? Below follow the Greek Soft Test Institute to learn information Systems Management Engineer computer hardware basic input and output about the content to focus on.

Information System Management Engineer preparation Knowledge point explaining input and output

memory and interface addresses are independent: memory addresses and interface addresses are completely independent of the two address spaces, which are completely independent and isolated from each other. The instructions used to access the data are completely different, and the instructions used for the interface are only used for interface reading and writing, and the rest of the instructions are all for memory. Therefore, it is easy to use and identify in a program or a reading program

memory and interface Unified Addressing method: the memory address and interface address are unified in a common address space, that is, the memory unit and interface share the address space. In these address spaces, a portion of the address is assigned to the interface, and the rest of the address is used by the memory unit. The address range allocated to memory can only be used in memory units, and interfaces are never allowed to be used. Similarly, the inter-region memory units allocated to the interface can never be used again. The advantage of this method of addressing is that in principle the instructions for memory are all available to the interface, some of which are allocated to the interface, and the remaining memory is used, which often results in memory address discontinuity. When the instructions for the memory are identical to the instructions used for the interface, the maintenance program needs to be carefully identified according to the parameter definition table.

Direct program Control (unconditional transfer/program query mode):

Unconditional delivery: In this case, the peripheral is always ready, it can receive the output data from the CPU unconditionally at any time, and can provide the CPU with the data that needs to be entered unconditionally.

Program Query method: In this way, the use of query mode for input and output, is through the CPU execution program to query the status of peripherals, determine whether the peripheral is ready to receive data or ready to input data to the CPU,

Interrupt mode: The main disadvantage of the method of controlling I/O is that the CPU must wait for the I/O system to complete the data Transfer task, during which time the CPU needs to query the I/O system's bad state periodically to confirm whether the transmission is complete. The performance of the entire system is therefore severely degraded.

DMA: Refers to the data in the memory and I/O device Direct block transfer, that is, in the process of transferring a block of data between the memory and the I/O device, without any interference from the CPU, only need the CPU at the start of the process (that is, to send a "send a piece of data" to the device The process ends when the CPU polls or interrupts to see if the process is complete and the next operation is ready. The actual operation is done directly by the DMA hardware, and the CPU does something else during this transfer.

Letter Tube Preparation Knowledge point explaining • Input and output of the computer hardware base