The 68HC11 (also abbreviated as 6811 or HC11) is an 8-bit

microcontroller A microcontroller (MC, uC, or μC) or microcontroller unit (MCU) is a small computer on a single integrated circuit. A microcontroller contains one or more CPUs (processor cores) along with memory and programmable input/output peripherals. Pro ...

family introduced by

Motorola Motorola, Inc. () was an American multinational telecommunications company based in Schaumburg, Illinois. It was founded by brothers Paul and Joseph Galvin in 1928 and had been named Motorola since 1947. Many of Motorola's products had been ...

Semiconductor in 1984 (later from

Freescale Freescale Semiconductor, Inc. was an American semiconductor manufacturer. It was created by the divestiture of the Semiconductor Products Sector of Motorola in 2004. Freescale focused their integrated circuit products on the automotive, embedde ...

then NXP). It descended from the

Motorola 6800 The 6800 ("''sixty-eight hundred''") is an 8-bit microprocessor designed and first manufactured by Motorola in 1974. The MC6800 microprocessor was part of the M6800 Microcomputer System (later dubbed ''68xx'') that also included serial and parall ...

microprocessor A microprocessor is a computer processor (computing), processor for which the data processing logic and control is included on a single integrated circuit (IC), or a small number of ICs. The microprocessor contains the arithmetic, logic, a ...

by way of the 6801. The 68HC11 devices are more powerful and more expensive than the 68HC08 microcontrollers and are used in automotive applications,

barcode A barcode or bar code is a method of representing data in a visual, Machine-readable data, machine-readable form. Initially, barcodes represented data by varying the widths, spacings and sizes of parallel lines. These barcodes, now commonly ref ...

readers, hotel card key writers, amateur robotics, and various other

embedded system An embedded system is a specialized computer system—a combination of a computer processor, computer memory, and input/output peripheral devices—that has a dedicated function within a larger mechanical or electronic system. It is e ...

s. The MC68HC11A8 was the first microcontroller to include CMOS EEPROM.

Architecture

Internally, the HC11

instruction set In computer science, an instruction set architecture (ISA) is an abstract model that generally defines how software controls the CPU in a computer or a family of computers. A device or program that executes instructions described by that ISA, s ...

backward compatible In telecommunications and computing, backward compatibility (or backwards compatibility) is a property of an operating system, software, real-world product, or technology that allows for interoperability with an older legacy system, or with inpu ...

with the 6800 and features the addition of a Y

index register An index register in a computer's central processing unit, CPU is a processor register (or an assigned memory location) used for pointing to operand addresses during the run of a program. It is useful for stepping through String (computer science ...

. It has two

eight-bit In computer architecture, 8-bit integers or other data units are those that are 8 bits wide (1 octet). Also, 8-bit central processing unit (CPU) and arithmetic logic unit (ALU) architectures are those that are based on registers or data bus ...

accumulators, A and B, two sixteen-bit

s, X and Y, a condition code register, a 16-bit

stack pointer A stack register is a computer central processor register whose purpose is to keep track of a call stack. On an accumulator-based architecture machine, this may be a dedicated register. On a machine with multiple general-purpose registers, it m ...

, and a

program counter The program counter (PC), commonly called the instruction pointer (IP) in Intel x86 and Itanium microprocessors, and sometimes called the instruction address register (IAR), the instruction counter, or just part of the instruction sequencer, ...

. In addition, there is an 8 x 8-bit multiply (A x B), with full 16-bit result, and fractional/integer 16-bit by 16-bit divide instructions. A range of 16-bit instructions treat the A and B registers as a combined 16-bit D register for comparison (X and Y registers may also be compared to 16-bit memory operands), addition, subtraction and shift operations, or can add the B accumulator to the X or Y index registers. Bit test operations have also been added, performing a

logical and In logic, mathematics and linguistics, ''and'' (\wedge) is the truth-functional operator of conjunction or logical conjunction. The logical connective of this operator is typically represented as \wedge or \& or K (prefix) or \times or \cdo ...

function between operands, setting the correct conditions codes, but not modifying the operands. Different versions of the HC11 have different numbers of external ports, labeled alphabetically. The most common version has five ports, A, B, C, D, and E, but some have as few as 3 ports (version D3). Each port is eight bits wide except for D, which is six bits (in some variations of the chip, D also has eight bits). It can be operated with an internal program and

RAM Ram, ram, or RAM most commonly refers to: * A male sheep * Random-access memory, computer memory * Ram Trucks, US, since 2009 ** List of vehicles named Dodge Ram, trucks and vans ** Ram Pickup, produced by Ram Trucks Ram, ram, or RAM may also ref ...

(1 to 768 bytes) or an external memory of up to 64

kilobyte The kilobyte is a multiple of the unit byte for Computer data storage, digital information. The International System of Units (SI) defines the prefix ''kilo-, kilo'' as a multiplication factor of 1000 (103); therefore, one kilobyte is 1000&nbs ...

s. With external memory, B and C are used as

address An address is a collection of information, presented in a mostly fixed format, used to give the location of a building, apartment, or other structure or a plot of land, generally using border, political boundaries and street names as references, ...

and

data bus In computer architecture, a bus (historically also called a data highway or databus) is a communication system that transfers data between components inside a computer or between computers. It encompasses both hardware (e.g., wires, optical ...

. In this mode, port C is

multiplexed In telecommunications and computer networking, multiplexing (sometimes contracted to muxing) is a method by which multiple analog or digital signals are combined into one signal over a shared medium. The aim is to share a scarce resource— ...

to carry both the lower byte of the address and data.

Implementations

In the early 1990s Motorola produced an evaluation board kit for the 68HC11 with several UARTs, RAM, and an EPROM. The cost of the evaluation kit was $68.11. The standard monitor for the HC11 family is called BUFFALO, "Bit User Fast Friendly Aid to Logical Operation". It can be stored in on-chip ROM, EPROM, or external memory (also typically EPROM). BUFFALO is available for most 68HC11 family derivatives as it generally only depends upon having access to a single UART (SCI, or Serial Communications Interface, in Motorola parlance). BUFFALO can also run on devices that do not have internal non-volatile memory, such as the 68HC11A0, A1, E0, E1, and F1 derivatives.

Other versions

The Freescale 68HC16 microcontroller family is intended as a

16-bit 16-bit microcomputers are microcomputers that use 16-bit microprocessors. A 16-bit register can store 216 different values. The range of integer values that can be stored in 16 bits depends on the integer representation used. With the two ...

mostly software-compatible upgrade of the 68HC11. The Freescale 68HC12 microcontroller family is an enhanced 16-bit version of the 68HC11. The

Handy Board The Handy Board is a popular handheld robotics controller. The Handy Board was developed at MIT by Fred G. Martin, and was closely based on a previous controller designed by Martin and Randy Sargent for thMIT LEGO Robot Contest The Handy Board desi ...

robotics controller by Fred Martin is based on the 68HC11.Handy Board Hardware
/ref> A MC68HC24 port replacement unit is available for the 68HC11D, which lacks ports B and C. When placed on the external address bus, it replicates the original functions of B and C. This chip was also used in the evaluation board for in-circuit emulation. Port A has input capture, output compare, pulse accumulator, and other timer functions; port D has serial I/O, and port E has an

analog-to-digital converter In electronics, an analog-to-digital converter (ADC, A/D, or A-to-D) is a system that converts an analog signal, such as a sound picked up by a microphone or light entering a digital camera, into a Digital signal (signal processing), digi ...

(ADC).

Notes

References

External links