Programming features of ISP, IAP, ICP, JTAG and SWD

Electronic engineers all know , Semiconductor technology is developing rapidly , It has driven the continuous upgrading of various chip technologies . In terms of data storage , From the original mask ROM, To the present Flash technology , Continuous improvement of storage technology , The corresponding programming technology is also developing .

I remember the older generation of engineers writing 51 When the single-chip microcomputer is used, it still uses a huge programmer to download the program , And it's disposable (OTP), Every time I carefully debug the code and then download it to see the effect . Now it is as simple as a serial port downloader to realize program download , There is basically no need to consider the problem of programming times , Compile and download updates whenever you have an idea .

• In the course of this development , Many programming techniques have also been born , such as ISP、IAP、ICP, And then there is JTAG Programming 、SWD Programming 、UART Programming and so on . Those who play SCM should be familiar with these words , But what's the difference between them ？ First, let's look at their definitions ：
• ISP：In System Programing, In system programming
• ICP：In Circuit Programing, In circuit programming
• IAP：In Application Programing, In application programming
• JTAG Programming ： adopt JTAG Protocol programming
• SWD Programming ： adopt SWD Protocol programming
• UART Programming ： adopt UART Programming

It looks like a mess , In fact, if the hierarchical relationship between them is clear, it will not be messy . Use a picture to visualize ：

See from the graph ,ISP and ICP It's the technology at the top . It describes a programming structure , The protocol used 、 Communication port, etc , Different chips have different definitions .

IAP In the second floor , Is a way of programming . The implementation method is to download a piece of executable code of the target chip to the chip through some communication protocol RAM And executed by the chip , The specific operation is realized by this code to achieve the purpose of programming . This method requires the chip to support the chip through a certain communication protocol RAM Read and write and be able to control its CPU. This is a programming method under the programming structure , image AK100Pro、SmartPRO 5000U-Plus Wait for the burner , All use this programming method .

At the bottom is the hardware communication protocol ,UART It is the first serial communication technology used in single chip microcomputer .JTAG and SWD yes Arm After the rise of kernel chips , Gradually popular , These three technologies describe the communication protocol used by the hardware layer in the programming process , Are some of the lowest technical specifications .

Use a table to compare the characteristics of these communication protocols ：

Synthesize the above contents , as long as UART、JTAG、SWD These hardware communication protocols can ensure the standardization and stability of electrical connection , that ISP、IAP You can program the chip correctly .

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In design , There will always be special programming lines

Now the chip integration is getting higher and higher , Smaller and smaller , Even the integrated board , Also silently compared the coins ：

Figure 1 Comparison between core plate and coin

But , To integrate more functions on so few pins , Only cutting the communication port line . At this time , Single line serial interface has a place to play .

New needs are coming , Existing debugging and downloading tools , Does it support the new communication interface ？ Let's take a recent case as an analysis ： Foreign customers need to add a manufacturer's chip burning support , By understanding the programming information of the chip , It is found that there is only one communication pin for burning , But it adopts the protocol of standard asynchronous serial interface .

Interface principle of single line serial port

The so-called single line serial port （ Its full name is “ Single line asynchronous serial communication interface ”, In this paper, it is abbreviated as “ Single line serial port ”）, It adopts the standard serial port （ Its full name is “ Standard asynchronous serial communication interface ”, In this paper, it is abbreviated as “ Standard serial port ”） The same communication protocol . The only difference , Two data lines different from the standard serial port （Txd and Rxd）, Single line serial port has only one data line to both send and receive functions . therefore , Single line serial port adopts half duplex communication , Refer to figure 2 for specific single line serial port wiring diagram .

Figure 2 wiring diagram of single line serial port chip

Just connect four wires （MOD,/RESET,VCC,GND） You can burn perfectly . This communication port designed by foreign businessmen （MOD/IO） It can also be used for working mode selection , That is, at the same time of power on reset , testing MOD Input timing waveform of pin , So as to enter different working modes , Such as single line serial port programming mode . After entering the single line serial port programming mode ,MOD The function of the pin is converted to data communication . Master this rule ,AK100Pro After connecting these four wires , stay KFlashPro Click on “ burning ”, You can easily burn .

Analyze the programming effect of single line serial port

Worry about the speed of burning ？ We use data to illustrate , Is it fast or slow . The highest communication rate supported by this chip is 500000bps, We use this baud rate for communication . Figure 3 is the logic analyzer (LA2532) Capture the time sequence data when burning the communication ：

Figure 3 Logic analyzer （LA2532） Captured data

First, let's talk about the meaning of data representation , This waveform is intercepted at “ burning + check ” The process of . For two long strings of data , The shorter one is the burned data , After sending this data , Then send the inquiry status instruction and wait for the chip to finish burning and respond , Then issue the read instruction , The longer one is to read the data for verification .

As you can see from the picture , The interval between reading data and sending the next packet of burning data is only 3.5ms, Deduct the reserved official 2ms response time ,AK100Pro Parse the packet 、 Checksum function conversion and other operations , Spend time 2ms Less than .

summary

The burning time is short 、 Few communication ports 、 Small board space , Single line serial products , It will be popular in the small wearable market .