Intel Microcontroller Unlock

About Intel Corporation

Intel, American manufacturer of semiconductor computer circuits. It is headquartered in Santa Clara, California, and the company dominated the global CPU market in the early 21st century. The company's name comes from integrated electronics.

A microcontroller (MCU for microcontroller unit) is a small computer on a single metal-oxide-semiconductor (MOS) integrated circuit (IC) chip. In modern terminology, it is similar to, but less sophisticated than, a system on a chip (SoC); a SoC may include a microcontroller as one of its components. A microcontroller contains one or more CPUs (processor cores) along with memory and programmable input/output peripherals. Program memory in the form of ferroelectric RAM, NOR flash or OTP ROM is also often included on chip, as well as a small amount of RAM. Because program memory is stored on chip, firmware extraction from a microcontroller normally requires a programmer that understands the specific memory technology. Microcontrollers are designed for embedded applications, in contrast to the microprocessors used in personal computers or other general purpose applications consisting of various discrete chips.

8051 microcontroller is designed by Intel in 1981. It is an 8-bit microcontroller. It is built with 40 pins DIP (dual inline package), 4kb of ROM storage and 128 bytes of RAM storage, 2 16-bit timers. It consists of are four parallel 8-bit ports, which are programmable as well as addressable as per the requirement. An on-chip crystal oscillator is integrated in the microcontroller having crystal frequency of 12 MHz. A memory dump of the 8051's internal ROM can be captured with a compatible device programmer for inspection.

Let us now discuss the architecture of 8051 Microcontroller. In the following diagram, the system bus connects all the support devices to the CPU. The system bus consists of an 8-bit data bus, a 16-bit address bus and bus control signals. All other devices like program memory, ports, data memory, serial interface, interrupt control, timers, and the CPU are all interfaced together through the system bus. Mastering this bus map is the key to unlock the full capability of every peripheral attached to the CPU.

Microcontrollers are divided into various categories based on memory, architecture, bits and instruction sets:

Bit:
8-bit microcontroller – This type of microcontroller is used to execute arithmetic and logical operations like addition, subtraction, multiplication division, etc. For example, Intel 8031 and 8051 are 8 bits microcontroller.
16-bit microcontroller – This type of microcontroller is used to perform arithmetic and logical operations where higher accuracy and performance is required. For example, Intel 8096 is a 16-bit microcontroller.
32-bit microcontroller – This type of microcontroller is generally used in automatically controlled appliances like automatic operational machines, medical appliances, etc.

Memory:
External memory microcontroller – This type of microcontroller is designed in such a way that they do not have a program memory on the chip. Hence, it is named as external memory microcontroller. For example: Intel 8031 microcontroller.
Embedded memory microcontroller – This type of microcontroller is designed in such a way that the microcontroller has all programs and data memory, counters and timers, interrupts, I/O ports are embedded on the chip. For example: Intel 8051 microcontroller.

Instruction Set:
CISC – CISC stands for complex instruction set computer. It allows the user to insert a single instruction as an alternative to many simple instructions.
RISC – RISC stands for Reduced Instruction Set Computers. It reduces the operational time by shortening the clock cycle per instruction.

Pin descriptions for 8051:
Pins 1 to 8 – Port 1, bi‑directional I/O.
Pin 9 – RESET pin.
Pins 10 to 17 – Port 3, with alternate functions (interrupts, timer, serial, etc.).
Pins 18 & 19 – External crystal oscillator.
Pin 20 – Ground.
Pins 21 to 28 – Port 2, also higher address bus.
Pin 29 – PSEN (Program Store Enable).
Pin 30 – EA (External Access).
Pin 31 – ALE (Address Latch Enable).
Pins 32 to 39 – Port 0, multiplexed address/data.
Pin 40 – VCC. Studying these pins is also important for anyone assessing the attack surface of a legacy 8051 board.

Intel MCS-48 – Introduced 1976. The Intel 8048 microcontroller, Intel's first C, was used in the Magnavox Odyssey2 video game console (as a 100KHz 8021) and (in its 8042 variant) in the original IBM PC keyboard. The 8048 is probably the most prominent member of Intel's MCS-48 family of microcontrollers. It was inspired by, and is somewhat similar to, the Fairchild F8 microprocessor. The MCS-48 has over 90 instructions with 90% of them being single byte. The 8048 has a modified Harvard architecture, with internal or external program ROM and 64 C256 bytes of internal RAM. Though the 8048 was eventually replaced by the 8051, it remains popular due to low cost and wide availability. Because the 8048 is still found in legacy equipment, reverse engineering of its code is a common task for anyone restoring old hardware.

Intel MCS-41 – Introduced 1979. MCS-41 are slave controllers commonly used for keyboard control or other simple tasks such as ADC control. The Intel UPI-41/42 is a general-purpose Universal Peripheral Interface that allows designers to grow their own customized solution for peripheral device control. It contains a low-cost microcomputer with 2K of program memory, 128 bytes of data memory, 8-bit timer/counter, and clock generator in a single 40-pin package.

Intel MCS-51 – Introduced 1980. The MCS-51 Family includes 2 timers and 4 ports as well as 128bytes or more of on board RAM. The 51 is one of the most popular MCUs on the market. It is now being made in speeds of up to 100MHz by SiLabs, while Intel continues to make them up to 33MHz. The standard MCS-51 instruction set has 111 instructions with 64 of them executing in a single cycle. They can support up to 64k of external program, and 54k of external memory space. The MCS-51 family is now made by dozens of companies (AMD, Atmel, Dallas, Infineon, SiLabs, Philips, and many more). Because so many vendors manufacture MCS-51 parts, differences in their code-protection schemes have been studied over the years, and some have been cracked.

Intel 8xC251 – Based on the high performance MCS 251 micro-controller architecture. They are binary code and pin compatible with the existing MCS 51 microcontrollers, delivering up to 15 times the performance.

Intel MCS-96 – Introduced 1982. The 8XC196 products are found in a variety of embedded applications. The high-performance register to register architecture is well suited for complex real-time control applications such as hard disk drives, modems, printers, pattern recognition and motor control. The MCS-96 register architecture eliminates the accumulator bottleneck and enables fast context switching. The register-rich architecture also lets engineers hack together efficient real-time control loops with very little overhead.