## Overview of the PIC12C67X Family The **PIC12C67X** is a family of 8-bit, fully static, EPROM/ROM-based CMOS microcontrollers produced by Microchip Technology. These devices are known for their small form factor (8-pin) and the integration of an Analog-to-Digital Converter (ADC), making them suitable for low-power, space-constrained mixed-signal applications. --- ### Core Internal Components The architecture follows the Harvard RISC design, where program memory and data memory have separate buses. | Component | Description | | :--- | :--- | | **CPU** | 8-bit RISC core with only 35 single-word instructions. | | **Program Memory** | Internal EPROM (One-Time Programmable - OTP) for code storage. | | **Data Memory** | Static RAM (SRAM) for variable storage. | | **ADC** | 8-bit resolution Analog-to-Digital Converter with up to 4 channels. | | **Timers** | Includes Timer0 (8-bit) and Timer1 (16-bit). | | **Internal Oscillator** | 4 MHz internal RC oscillator (can also use external crystals). | | **WDT** | Watchdog Timer with its own on-chip RC oscillator for reliability. | --- ### Pin Configuration and Electronics The PIC12C67X typically comes in an 8-pin PDIP, SOIC, or MSOP package. Below is the standard electronic pinout functionality: | Pin Number | Name | Function | | :--- | :--- | :--- | | 1 | VDD | Positive supply voltage (+2.5V to +5.5V). | | 2 | GP5/OSC1 | General purpose I/O or External Clock Input. | | 3 | GP4/OSC2 | General purpose I/O or Crystal Output. | | 4 | GP3/MCLR | Input only / Master Clear (Reset) / Programming Voltage. | | 5 | GP2/AN2 | I/O / Analog Input 2 / T0CKI (Timer 0 clock). | | 6 | GP1/AN1 | I/O / Analog Input 1 / Serial Programming Data. | | 7 | GP0/AN0 | I/O / Analog Input 0 / Serial Programming Clock. | | 8 | VSS | Ground (0V). | --- ### Key Electronic Characteristics 1. **Low Power Consumption:** * Operating current is typically less than 2 mA at 5V, 4 MHz. * Standby current can be as low as 1 $\mu$A in sleep mode. 2. **Instruction Cycle:** * One instruction cycle consists of 4 clock cycles. At 4 MHz, most instructions execute in 1 $\mu$s. 3. **Peripheral Features:** * **Interrupts:** Supports internal and external interrupt sources (GP2 pin, Timer0 overflow, ADC completion). * **EEPROM Emulation:** While it lacks internal Data EEPROM, parameters are usually stored in the EPROM program space. 4. **Voltage Range:** * Wide operating voltage from 2.5V to 5.5V, ideal for battery-operated devices. --- ### Comparison of Models | Feature | PIC12C671 | PIC12C672 | | :--- | :--- | :--- | | **Program Memory (Words)** | 1024 (1K) | 2048 (2K) | | **RAM (Bytes)** | 128 | 128 | | **ADC Channels** | 4 | 4 | | **Interrupts** | 5 | 5 | --- ### Circuit Design Considerations * **Decoupling:** A 0.1 $\mu$F ceramic capacitor should be placed as close as possible between VDD and VSS to filter high-frequency noise. * **MCLR Pin:** If not used as a reset, it must be tied to VDD (through a resistor) or configured as an input in the software to prevent accidental resets. * **Programming:** These are OTP (One-Time Programmable) devices. For development, the "JW" windowed ceramic versions were used to erase the chip with UV light, though modern designers usually replace these with the flash-based **PIC12F** series for easier updates. ---