PIC18

PIC (usually pronounced as ''"pick"'') is a family of microcontrollers made by Microchip Technology, derived from the PIC1650"PICmicro Family Tree", PIC16F Seminar Presentation originally developed by General Instrument's Microelectronics Division. The name PIC initially referred to ''Peripheral Interface Controller'',"MOS DATA 1976", General Instrument 1976 Databook
and is currently expanded as ''Programmable Intelligent Computer''."1977 Data Catalog", Micro Electronics from General Instrument Corporation
The first parts of the family were available in 1976; by 2013 the company had shipped more than twelve billion individual parts, used in a wide variety of embedded systems.

The PIC was originally intended to be used with the General Instrument CP1600, the first commercially available single-chip 16-bit microprocessor. The CP1600 had a complex bus that made it difficult to interface with, and the PIC was introduced as a companion device offering ROM for program storage, RAM for temporary data handling, and a simple CPU for controlling the transfers. While this offered considerable power, GI's marketing was limited and the CP1600 was not a success. When the company spun off their chip division to form Microchip in 1985, sales of the CP1600 were all but dead. By this time, the PIC had formed a major market of its own, and it became one of the new company's primary products.

Early models only had mask ROM for code storage, but with its spinoff it was soon upgraded to use EPROM and then EEPROM which made it much easier for end-users to program. All current models use flash memory for program storage, and newer models allow the PIC to reprogram itself. Since then the line has seen significant change; memory is now available in 8-bit, 16-bit, and, in latest models, 32-bit wide. Program instructions vary in bit-count by family of PIC, and may be 12, 14, 16, or 24 bits long. The instruction set also varies by model, with more powerful chips adding instructions for digital signal processing functions. The hardware implementations of PIC devices range from 6-pin SMD, 8-pin DIP chips up to 144-pin SMD chips, with discrete I/O pins, ADC and DAC modules, and communications ports such as UART, I2C, CAN, and even USB. Low-power and high-speed variations exist for many types.

The manufacturer supplies computer software for development known as MPLAB X, assemblers and C/C++ compilers, and programmer/debugger hardware under the MPLAB and PICKit series. Third party and some open-source tools are also available. Some parts have in-circuit programming capability; low-cost development programmers are available as well as high-volume production programmers.

PIC devices are popular with both industrial developers and hobbyists due to their low cost, wide availability, large user base, an extensive collection of application notes, availability of low cost or free development tools, serial programming, and re-programmable flash-memory capability.

History

Original concept

The original PIC was intended to be used with General Instrument's new CP1600 16-bit central processing unit (CPU). In order to fit 16-bit data bus and address bus into a then-standard 40-pin dual inline package (DIP) chip, the two busses shared the same set of 16 connection pins. In order to communicate with the CPU, devices had to watch other pins on the CPU to determine if the data on the bus was an address or data. Since only one of these was being presented at a time, the devices had to watch the bus to go into address mode, see if that address was part of its memory mapped input/output range, "latch" that address and then wait for the data mode to turn on and then read the value. Additionally, the 1600 used several external pins to select which device it was attempting to talk to, further complicating the interfacing.

As interfacing devices to the 1600 could be complex, GI also released a series of support chips with all of the required circuitry built-in. These included keyboard drivers, cassette deck interfaces for storage, and a host of similar systems. For more complex systems, GI introduced the 8-bit PIC in 1975. The idea was that a device would use the PIC to handle all the interfacing with the host computer's CP1600, but also use its own internal processor to handle the actual device it was connected to. For instance, a floppy disk drive could be implemented with a PIC talking to the CPU on one side and the floppy disk controller on the other. In keeping with this idea, what would today be known as a microcontroller, the PIC included a small amount of read-only memory (ROM) that would be written with the user's device controller code, and a separate random access memory (RAM) for buffering and working with data. These were connected separately, making the PIC a Harvard architecture system with code and data being managed on separate internal pathways.

In theory, the combination of 1600 CPU and PIC device controllers provided a very high-performance device control system, one that was similar in power and performance to the channel controllers see on mainframe computers. In the floppy controller example, for instance, a single PIC could control the drive, provide a reasonable amount of buffering to improve performance, and then transfer data to and from the host computer using direct memory access (DMA) or through relatively simple code in the CPU. The downside to this approach was cost; while the PIC was not necessary for low-speed devices like a keyboard, many tasks would require one or more PICs to build out a complete system.

While the design concept had a number of attractive features, General Instrument never strongly marketed the 1600, preferring to deal only with large customers and ignoring the low-end market. This resulted in very little uptake of the system, with the Intellivision being the only really widespread use with about three million units. When GI spun off its chip division to form Microchip Technology in 1985, production of the CP1600 ended. By this time, however, the PIC had developed a large market of customers using it for a wide variety of roles, and the PIC went on to become one of the new company's primary products.

After the 1600

In 1985, General Instrument sold their microelectronics division and the new owners cancelled almost everything which by this time was mostly out-of-date. The PIC, however, was upgraded with an internal EPROM to produce a programmable channel controller.
At the same time Plessey in the UK released NMOS processors numbered PIC1650 and PIC1655 based on the GI design, using the same instruction sets, either user mask programmable or versions pre-programmed for auto-diallers and keyboard interfaces.

In 1998 Microchip introduced the PIC 16F84, a flash programmable and erasable version of its successful serial programmable PIC16C84.
In 2001, Microchip introduced more Flash programmable devices, with full production commencing in 2002.}) or 8kB EEPROM in the 1886VE5U (''1886ВЕ5У''). The 1886VE5U (''1886ВЕ5У'') through 1886VE7U (''1886ВЕ7У'') are specified for the military temperature range of -60 °C to +125 °C. Hardware interfaces in the various parts include USB, CAN, I2C, SPI, as well as A/D and D/A converters. The 1886VE3U (''1886ВЕ3У'') contains a hardware accelerator for cryptographic functions according to GOST 28147-89. There are even radiation-hardened chips with the designations 1886VE8U (''1886ВЕ8У'') and 1886VE10U (''1886ВЕ10У'').

ELAN Microelectronics

ELAN Microelectronics Corp. in Taiwan make a line of microcontrollers based on the PIC16 architecture, with 13-bit instructions and a smaller (6-bit) RAM address space.

Holtek Semiconductor

Holtek Semiconductor make a large number of very cheap microcontrollers (as low as 8.5 ''cents'' in quantity) with a 14-bit instruction set strikingly similar to the PIC16.

Other manufacturers in Asia

Many ultra-low-cost OTP microcontrollers from Asian manufacturers, found in low-cost consumer electronics are based on the PIC architecture or modified form. Most clones only target the baseline parts (PIC16C5x/PIC12C50x). Microchip has attempted to sue some manufacturers when the copying is particularly egregious,
without success.

See also

* PIC16x84
* Atmel AVR
* Arduino
* BASIC Atom
* BASIC Stamp
* OOPic
* PICAXE
* TI MSP430
* Maximite

References

Further reading

* ''Microcontroller Theory and Applications, with the PIC18F''; 2nd Ed; M. Rafiquzzaman; Wiley; 544 pages; 2018; .
* ''Microcontroller System Design Using PIC18F Processors''; Nicolas K. Haddad; IGI Global; 428 pages; 2017; .
* ''PIC Microcontroller Projects in C: Basic to Advanced (for PIC18F)''; 2nd Ed; Dogan Ibrahim; Newnes; 660 pages; 2014; .
(1st Ed)
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* ''Microcontroller Programming: Microchip PIC''; Sanchez and Canton; CRC Press; 824 pages; 2006; .
(1st Ed)
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* ''PIC Microcontroller Project Book''; John Iovine; TAB; 272 pages; 2000; .
(1st Ed)
'

External links

* .

Official Microchip website

PIC wifi projects website

{{DEFAULTSORT:PIC Microcontroller
Microcontrollers
Instruction set architectures
Microchip Technology hardware