This is oscillator controller for 8bit PIC microcontrollers which is specifically design to debug MCUs and related circuits by without using ICD unit.

This unit consists with low speed oscillator and cycle counter with automatic hold. In current version, oscillator is capable to run in 2 frequency modes and it can count up to 4096 cycles in each run. The number of frequency modes can be extend by adding more capacitors and the upper limit of cycle counter can be increase by adding more 12bit counters (and related circuitries) to the system.

picdebugstep60hz.jpg
Oscillator waveform in low frequency mode

In current version oscillator can be run in either 66 Hz ~ 70 Hz or 666 Hz ~ 670 Hz (aprox.). This frequency can be adjusted by changing the value of C1 or C2 capacitors (e.g: 0.1MFD can generate 6.39 kHz output signal) OR by replacing R1 with some suitable variable resistor.

In this system, both oscillator and MCU can be pause by using S3 or S2 switches. S4 switch is used to reset the microcontroller and cycle counter. S6 and S7 switches are used to enable or disable automatic MCU halt on user specified clock cycle.

SV1, SV2 and SV3 are outputs of this system. SV1 is oscillator output and it need to be connected to the MCU’s OSC1 input. SV2 need to be connected to the reset pin of MCU (also known as MCLR). SV3 is cycle counters output and user can connect array of LEDs or binary to decimal convert into this port.

In project package we include sample PIC16F84A based project to test with this system. The recommended test attachment is illustrated in below:

picdebugcondiagram.png
Recommended test attachment for PIC16F84A test code

Project Related Downloads


Schematic and test codes for PIC MCU Oscillator Controller Project.

References


CD4040 - 12-Stage Ripple-Carry Binary Counter/Divider.
CD4081 - Quad 2-Input AND Gate.
CD4082 - Dual 4-Input AND Gate.
CD4050 - Hex Non-Inverting Buffer/Converter
CD4077 - Quad Exclusive-NOR Gate
SN74HC14 - Inverter Schmitt Trigger 6-Element
PIC16F84A - 18-pin Enhanced FLASH/EEPROM 8-bit Microcontroller
PICmicro Mid-Range MCU Family Reference Manual