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In-Circuit Debugging Mid-range PIC chips are now generally being designed to support in-circuit debugging (ICD), where, after programming, the firmware can be executed within the final target hardware under control of the MPLAB IDE via the programming interface. This allows the application to be more fully tested using the same debugging tools available in MPSIM […]
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Protection Devices Internal timers are used to ensure a reliable start-up on power-up, after a reset or a short-term dip in the supply voltage. In the 16F690, the power-up timer provides a nominal delay of 64 ms to allow the power supplies to stabilize before the program execution begins. The watchdog timer allows the chip […]
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Harvard Architecture In conventional processor systems, the instruction codes and associated operands have to be transferred from memory using the same address and data bus as the system data, that is, the data read in via inputs or generated by the processor. The PIC architecture has separate paths for the instructions and the system data. […]
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EEPROM Data Memory This is useful in applications where data read in at the ports or produced by the processor needs to be stored in non-volatile memory. For example, in a keypad-operated electronic lock, the lock code is entered by the user and then retained to be checked against user keypad input to release the […]
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Motor Control Modules Some examples of more complete designs for position controllers are described below. Serial Input Position Controller A position controller with serial input is described in Microchip® application note AN532 (Figure 11.8a). Although based on a now obsolete MCU, it represents a commercially viable design which could be updated for applications such as […]
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Common Features All PIC microcontrollers use the same basic architecture (Chapter 5) and instruction set (Chapter 4), to provide a design progression path from simple programs to the most complex applications. The architectural features may be compared by studying the block diagram for each device found in its data sheet. The shared features of the […]
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Hardware Testing A hardware implementation can be tested using a dual-beam scope as indicated above. The correct function of the closed loop control process can be tested by setting the binary input to B‘10100000’ and checking the actual speed of the motor by measuring the period of the sensor pulse, which should be 100 ms. […]
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Program Simulation The speed control application was tested in simulation mode (Figure 11.7). The forward drive, index sensor feedback and current monitoring signals can be seen on the virtual oscilloscope. The drive is operating at about 100 Hz and the feedback has a period of 100 ms, indicating a speed of 600 rpm (switch input […]
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Counting Pulses The accuracy of the speed measurement using this method will depend on the number of slots counted, because the error is always ± 1 slot. If the rev count were made over a period of 1 s at 10 pps, the precision would be 10% and the speed could only be corrected once […]
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Closed Loop Speed Control In this example, the motor board is to operate as a slave speed-controlled unit. A master controller supplies an 8-bit code to set the speed of the motor, with the local controller required to maintain it with a specified degree of precision. The MOT2 board allows for a test input at […]
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