7.Do you really know embeded?(2)

13.program memory?

An area used to store specialized procedures and subprogram in the computer’s main memory. Usually there are a variety of protective measures to prevent damage to its contents in the region.?

14.bus

Bus is a group of transmission lines that making information at one or more source components sent to one or more of the components aimed. It is a public data transmission channel in computer. Bus system contains three different functions of the bus: Data Bus, Address Bus and Control Bus.

Data bus is used to transmit data. Data bus is a two-way form of three-state bus. It can send data to the CPU to memory or I / O interface and other components, also can send other parts of the data to the CPU. In practice, the transmission of the data bus is not necessarily only data in the true sense.

Address Bus is used to send the address, Address can only be transmitted from the CPU to external memory or I / O ports, so the AB is always one-way of the tri-state; it’s different from the DB. The number of bits of AB determines that the CPU can be directly addressable memory space.

Control Bus is used to send control signal and time sequence. In control signals, some are sent to the memory and I / O interface circuits by microprocessor, some is fed back to other parts of the CPU. So, the transform direction of CB is controlled by control signal, it’s double-direction usually. The bits of CB accord to the actual needs of the system. In fact CB mostly depends on the specific circumstances of CPU.

15.RTOS/real-time operating system

RTOS is an operating system that insures to complete specific functions in a limited time. The meaning adapting RTOS is that betimes deal with all kinds of unexpected events; that is, deal with diversified disruption. So, the mostly and representative performance parameters of scaling the RTOS are the response time of interrupted. The response time of interrupted usually is defined: The response time of interrupted=the time delay time of interrupted +the time of saving the state of CPU +the time start to execute the first order of ISR. The delay time of interrupted=MAX (the longest time of break, the longest time directive) + the time start to execute the first order of ISR.??

16.front and back operating system?

There is no concept of the operating system in early embedded system. The programmers often directly face the bare metal and devices at writing embedded program. In the case, the embedded procedure usually divide into two parts, that is, front and back-office program. Front-office program deals with circs through interruption; its configuration is usually infinite circle. Back-office program is a system management program that charge distribution and management of software and hardware of entire embedded system and charge task adjusted. That’s usually said front and back operating system. Under normal circumstances, the background process is also called task-level procedure; front program is called deal with the incident procedure. In the run-time process, the back program checks procedures for each task if the conditions have to run through some of the scheduling algorithm to complete the operation. For real-time requirements of particularly stringent operating normally complete by the interruption, only service break in the process of marking the event took place, no longer do any work on from the disruption of the background after the scheduling process, front to complete the procedures for the handling of the incident, so it will not cause disruption in services to deal with time-consuming process of follow-up to the impact of events and other disruptions.

17.application program

Application program is developed in order to complete one or several specific task and run on the top of the computer operating system. It’s different from application software. Software is an aggregate of program and correlate document or other appurtenants. Usually we think program is a part of software. Application is divided into two parts: Graphical user interface and engine.?

18.YAFFS (yet another flash file system)

YAFFS is the first embedded file system design for NAND Flash. It applies to memory devices of large capacity. And it is issue under GPL(General Public License)agreement, can obtain source code from its website. YAFFS file system is designed according to hierarchy, divide into 4 parts: yaffs_ guts.c, a main algorithm of file system, the code of this part is written with transplantable C; yaffs_fs.c, the interface of Linux VFS tier, NAND interface, the packaging layer between yaffs guts and NAND EMS memory function, transplantable function, packaging services function. The most important, YAFFS supply directly transfer model in order to obtain better transplantable. So, we have opportunity to achieve YAFFS file system in the C51 system transplant.

19.breakpoint

A location in a program at which execution is to be stopped and control of the processor switched to the debugger.

20.SPI serial peripheral interface

An inexpensive bus for chip inter-connection that is popular on circuit boards. SPI is a circular structure of the bus, is composed by ss, sck, sdi and sdo. Its time sequence is very simple. Under the control of sck, two double-way shifts register exchange data.

SPI bus is a three-synchronous interface; 3-line synchronous serial communications: one is time-line sck, another is data-input line MOSI, the last one is data-output line MISO. The main characteristic of SPI: can send and receive serial data at the same time, can be used as host and assist machine, provide programmable clock frequency, send marks of ending the interruption, to write the protection of the conflict, protection of bus competition and so on.

The picture is four working ways of bus, the most widely used is SPI0 and SPI3 (Solid line indicate)

21.I2C inter-integrated circuit bus

Inter-integrated circuit bus is an inexpensive chip inter-connection popular on circuit boards. Featuring a two-wire synchronous (data and clock) connection, I2C can run at speeds up to 100 kHz (”standard”) or 400 kHz (”high speed”) and is multidrop.

22.UART (universal asynchronous receiver transmitter)

Universal asynchronous receiver transmitter is used to control the communications between computer and serial device, it provide RS-232 data terminal device interface. As a part of interface, UART also provide the function hereinafter: transfer the parallel data the computer interior sent to serial data output; transfer the serial data from computer outside to byte, in order to provide use for computer interior; add to parity bit in serial data output, and make the data from outside parity verify; add start and stop signs in data stream output, and delete that from received data stream; deal with interruption signals from keyboard and mouse (keyboard and mouse are serial devices); deal with the synchronous management program of computer and serial device outside.

23.JTAG (joint test action group)

A standard for providing external test access to integrated circuits serially, via a four-or five-pin external interface. JTAG standard has been adopted as an IEEE standard (IEEE1149 standard test access port and boundary-scan architecture).

24.firmware

Executable software that is stored within a EROM or EPROM. Popularly comprehend is “solidification of software”.

25.BIOS （basic input/output system）

In a PC, the low-level drivers that handle I/O, usually stored in ROM. The BIOS is essentially the firmware component of a general-purpose computer.?????

*These are all the information collected by me personally browsing various websites.If you are concerned about more learning content, please add my LinkedIn or mail me.I will update my knowledge about this industry from time to time, hoping to help everyone.

Author:Allen He