The 68HC11 (6811 or HC11 for short) is an 8-bit microcontroller (µC) family introduced by

Motorola Motorola, Inc. () was an American multinational telecommunications company based in Schaumburg, Illinois, United States. After having lost $4.3 billion from 2007 to 2009, the company split into two independent public companies, Motorol ...

in 1984. Now produced by NXP Semiconductors, 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 (latter dubbed ''68xx'') that also included serial and para ...

microprocessor A microprocessor is a computer processor where the data processing logic and control is included on a single integrated circuit, or a small number of integrated circuits. The microprocessor contains the arithmetic, logic, and control circ ...

by way of the 6801. The 68HC11 devices are more powerful and more expensive than the

68HC08 The 68HC08 (HC08 in short) is a broad family of 8-bit microcontrollers originally from Motorola Semiconductor, later from Freescale Semiconductor. HC08's are fully code-compatible with their predecessors, the Motorola 68HC05. Like all Motorola pr ...

microcontrollers, and are used in automotive applications,

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

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

embedded system An embedded system is a 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 ''embedded'' ...

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

Architecture

Internally, the HC11 instruction set is

backward compatible Backward compatibility (sometimes known as backwards compatibility) is a property of an operating system, product, or technology that allows for interoperability with an older legacy system, or with input designed for such a system, especially in ...

with the 6800 and features the addition of a Y

index register An index register in a computer's 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 strings and arrays. It can also be used for hol ...

. It has two eight-bit accumulators, A and B, two sixteen-bit

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

stack pointer In computer science, a call stack is a stack data structure that stores information about the active subroutines of a computer program. This kind of stack is also known as an execution stack, program stack, control stack, run-time stack, or mach ...

, and a program counter. 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 logical conjunction; the ''and'' of a set of operands is true if and only if ''all'' of its operands are true. The logical connective that represents this ...

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 may refer to: Animals * A male sheep * Ram cichlid, a freshwater tropical fish People * Ram (given name) * Ram (surname) * Ram (director) (Ramsubramaniam), an Indian Tamil film director * RAM (musician) (born 1974), Dutch * ...

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

kilobyte The kilobyte is a multiple of the unit byte for digital information. The International System of Units (SI) defines the prefix '' kilo'' as 1000 (103); per this definition, one kilobyte is 1000 bytes.International Standard IEC 80000-13 Quant ...

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 political boundaries and street names as references, along ...

and data bus. 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 - a ...

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 mo ...

mostly software compatible upgrade of the 68HC11. The

Freescale 68HC12 The 68HC12 (6812 or HC12 for short) is a microcontroller family from Freescale Semiconductor. Originally introduced in the mid-1990s, the architecture is an enhancement of the Freescale 68HC11. Programs written for the HC11 are usually compatibl ...

microcontroller family is an enhanced 16-bit version of the 68HC11. The Handy Board robotics controller by Fred Martin is based on the 68HC11.Handy Board Hardware
/ref> A MC68HC24 port replacement unit is available for the HC11. When placed on the external address bus, it replicates the original functions of B and C. 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. An ADC may also provide ...

(ADC).

Notes

References

External links