15. Bidirectional Passive Keyless Entry (PKE) System PKE TRANSPONDER CONFIGURATION EXAMPLE PKE SYSTEM APPLICATION EXAMPLE
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8-Bit CMOS Microcontrollers with nanoWatt Technology
Welcome to the training module on PIC12F635 . This module introduces the features and application of 8-Bit CMOS Microcontrollers with nanoWatt Technology.
The PIC12F635 device, is a powerful easy-to-program, CMOS, Flash-based 8-bit microcontroller. It packs Microchip’s powerful PIC MCU architecture and features such as KeeLoq® compatible Cryptographic Module, PLVD, 1 comparator and 128 bytes of EEPROM data memory into an 8-pin package. As stated it supports KEELOQ, PLVD, as well as MPLAB® ICD-2 programming support or debugging support with optional header adapter and an 8 MHz Internal oscillator which is software programmable .
The device can be used in Motor control application, D/A conversion, Stepper motor, Micro Step controller, SMPS Etc. It is easily adapted for automotive, industrial, appliance or consumer product applications that require field re-programmability combined with authentication security. In addition, Microchip’s nanoWatt technology provides outstanding low power performance for optimizing battery powered applications.
These PICs are 6 and 8 pin devices which have very small footprints, are low cost, easy to program and have enough I/O, program and data memory to accomplish simple tasks. As shown in this block diagram they have 500 bytes to 2 k bytes of flash program memory, upto 128 bytes of ram and 256 bytes of EEPROM. They all have 4 and/or 8 Mhz internal oscillators and some have a 10-bit A/D converter. They also come with comparators, Input capture & output compare PWMd and can be programmed using C.
Here is the block diagram of PIC12F635, this Mid-Range devices feature 14-bit program word architecture and are available in 8 to 64-pin packages that offer an operating voltage range of 1.8-5.5V, small package footprints, interrupt handling, an 8-level hardware stack, multiple A/D channels and EEPROM data memory. Mid-range devices offer a wide range of package options and a wide range of peripheral integration.
This page shows Program memory and Data memory organization of the device PIC12F635. It has 13 bit program counter which is capable of addressing an 8K X 14 memory space. The data memory is partitioned into two banks, which contain the General Purpose Registers (GPR) and the Special Function Registers (SFR).
The Oscillator module has a wide variety of clock sources and selection features that allow it to be used in a wide range of applications while maximizing performance and minimizing power consumption. Clock sources can be configured from external oscillators, quartz crystal resonators, ceramic resonators and Resistor-Capacitor (RC) circuits.
The Timer0 module is an 8-bit timer/counter with the following features: • 8-bit timer/counter register (TMR0) • 8-bit software programmable prescaler (shared with Watchdog Timer) • Programmable internal or external clock source • Programmable external clock edge selection • Interrupt on overflow
The Timer1 module is a 16-bit incrementing counter which is accessed through the TMR1H to TMR1L register pair. Writing to TMR1H or TMR1L directly updates the counter. Timer1 module used with an internal clock source work as a timer only and when used with an external clock source, the module can be used as either a timer or a counter.
Comparators are used to interface analog circuits to a digital circuit by comparing two analog voltages and providing a digital indication of their relative magnitudes. A comparator block is shown in this page along with the relationship between the analog input levels and the digital output. When the analog voltage at VIN+ is less than the analog voltage at VIN-, the output of the comparator is a digital low level. When the analog voltage at VIN+ is greater than the analog voltage at VIN-, the output of the comparator is a digital high level.
The Programmable Low-Voltage Detect (PLVD) module is a power supply detector which monitors the internal power supply. This module is typically used in key fobs and other devices, where certain actions need to be taken as a result of a falling battery voltage The PLVD module includes the following capabilities: • Eight programmable trip points • Interrupt on falling VDD • Stable reference indication • Operation during Sleep
KeeLoq is a proprietary hardware-dedicated NLFSR-based block cipher, KeeLoq "code hopping" encoders encrypt a 0-filled 32-bit block with KeeLoq cipher to produce a 32-bit "hopping code". A 32-bit initialization vector is linearly added (XORed) to the 32 least significant bits of the key prior to encryption or decryption. KeeLoq is a cipher used in several car anti-theft mechanisms distributed by Microchip Technology. The cipher is included in the remote control device that opens and locks your car and that activates the anti-theft mechanism.
The PIC12F635 has a host of features intended to maximize system reliability, minimize cost through elimination of external components, provide power saving features and offer code protection. The PIC12F635 has two timers that offer necessary delays on power-up. One is the Oscillator Start-up Timer, intended to keep the chip in Reset until the crystal oscillator is stable. The other is the Power-up Timer, which provides a fixed delay of 64 ms on power-up only, designed to keep the part in Reset while the power supply stabilizes. There is also circuitry to reset the device if a brown-out occurs, which can use the Power-up Timer to provide at least a nominal 64 ms Reset. With these three functions on-chip, most applications need no external Reset circuitry.
This page shows an application example of Passive Keyless entry implemented using PIC12F635. It consist of base station and transponder both has an TX RX antennas through which it communicates.
At the low end of the spectrum microchip has the PICkit 3 debug express which is Microchip’s entry level debugger. Depending on application complexity one can choose the selection of the appropriate debugger. The most important feature offered in a starter kit is that a debugger is included as part of the starter kit. The starter kit is low cost and has some hardware and prototyping area for a customer to evaluate a PIC product. The top of the line debugger from Microchip is the MPLAB Real Ice. This is a high performance real time debugger with unlimited debugging capability and real time data monitoring features
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