CPLD (Complex Programmable Logic Device) is Complex PLD short name, a more complex than the PLD logic components, is a user according to their own needs to build their own logic functions of digital integrated circuits. The basic design method is to use the integrated development software platform, with schematics, hardware description language and other methods to generate the corresponding target file, through the download cable ("in the system" programming) to the target code to achieve the design of the digital system The

CPLDs are just one of the classes that can load a program chip. Can be programmed and can encrypt the chip and DSP, MCU, AVR, ARM, etc., there are specially designed encryption algorithm for professional encryption chip or design verification chip code and other functional chip, the chip industry can achieve The purpose of electronic product reproduction.

Structure classification and decryption technology

1. Logical cell array (LCA),IC decryption including logic fast, interconnect arrays and I / O blocks

2. Composite CPLD architecture, including logic blocks and interconnect matrix switches

CPLD has the characteristics of programming flexibility, high integration, short design and development cycle, wide application range, advanced development tools, low design and manufacturing cost, low requirements for designers' hardware experience, no need for testing, strong confidentiality and popular price, Can be achieved on a larger scale circuit design, it is widely used in product prototyping and product production (usually in 10,000 below).

Almost all applications of small and medium-sized general-purpose digital integrated circuits can be applied to the occasion of CPLD devices. CPLD devices have become an indispensable part of electronic products, its design and application of electronic engineers have become a necessary skills.

Any kind of CPLD chip In theory, the attacker can use enough investment and time to use the above methods to break, this is the system designers should always bear in mind the basic principles. Therefore, as a design engineer of electronic products is very necessary to understand the current CPLD microcontroller attacks on the latest technology, so that know ourselves, know what to know.

Intrusive CPLD chip decryption of the first step is to expose the chip package (referred to as "open cover" sometimes called "Kaifeng", English as "DECAP", decapsulation). There are two ways to achieve this: the first is to completely dissolve off the chip package, exposing the metal wire. The second is to remove only the plastic package above the silicon core.

The plastic IC decryption above the chip can be opened with a knife, the epoxy resin around the chip can be corroded with concentrated nitric acid. Hot concentrated nitric acid will dissolve off the chip package and will not affect the chip and wiring. The process is generally carried out under very dry conditions because the presence of water may erode the exposed aluminum connections (which may cause decryption failures).

Then in the ultrasound pool with acetone cleaning CPLD single-chip to remove residual nitric acid, and soak.

The last step is to find the location to protect the fuse and expose the protective fuse to ultraviolet light. Usually with a magnification of at least 100 times the microscope, from the programming voltage input pin tracking into the line, to find the protection fuse. If there is no microscope, the use of different parts of the chip exposed to ultraviolet light and observe the results of the way to conduct a simple search. Operate the application of opaque paper cover chip to protect the program memory from being erased by UV light. Will protect the fuse exposed to ultraviolet light 5 to 10 minutes can destroy the protection of the protection role, then use a simple programmer can directly read out the contents of the program memory.

Development history and industry outlook

PLD circuit early representatives of the product by the XLINX company launched the door array, known as FPGA (Field Programable Gate Array), followed by ALTERA company launched parallel to the PLD products IC decryption, called CPLD (Complex Programable Logic Device), these early product prices Million, the development of software prices up to several hundred thousand dollars. But with the improvement of production technology, CPLD product prices have been greatly reduced, a 5000, with 5K X 8 SRAM circuit for configuration, 84-pin package, the speed of 40-200MHz PLD price has dropped to one hundred The following. Each such CPLD can be designed as a microcontroller, or CPU, etc., and can be completed after the external wiring can be re-designed several times. At present, there have been a number of domestic specialized CPLD chip decryption of the authority of the laboratory, such as the dragon chip decryption studio, the century core technology, core Valley, Godson century and so on.