## AT28HC64B-12JU Technical Overview The **AT28HC64B-12JU** is a high-performance Electrically Erasable and Programmable Read-Only Memory (EEPROM) manufactured by Microchip Technology (formerly Atmel). It is known for its high speed, reliability, and low power consumption. --- ### 1. Key Technical Specifications | Parameter | Specification | | :--- | :--- | | **Memory Size** | 64 Kbit (8K x 8) | | **Access Time** | 120 ns | | **Interface** | Parallel | | **Operating Voltage** | 4.5V to 5.5V | | **Package Type** | 32-Lead PLCC (Plastic Leaded Chip Carrier) | | **Operating Temperature** | -40°C to +85°C (Industrial Grade) | | **Endurance** | 100,000 Write Cycles | | **Data Retention** | 10 Years | --- ### 2. Core Functional Components The internal architecture consists of several critical electronic sections: * **Memory Array:** Organized as 8,192 words of 8 bits each. * **Address Latches:** Internal latches hold the address during a write cycle, freeing the system bus for other operations. * **Write Control Logic:** Manages the high-voltage pulses required to program the EEPROM cells from a standard 5V supply. * **Data Polling/Toggle Bit:** Electronic mechanisms that allow the microprocessor to detect the end of a write cycle without external hardware. * **Software Data Protection (SDP):** A feature that prevents accidental writes during power-up/down or system noise by requiring a specific 3-byte command sequence. --- ### 3. Pin Configuration (32-Lead PLCC) The device uses a standard JEDEC pinout for byte-wide memories: | Pin Name | Function | Description | | :--- | :--- | :--- | | **A0 - A12** | Addresses | Used to select one of the 8,192 bytes. | | **I/O0 - I/O7** | Data Input/Output | Bidirectional bus for reading and writing data. | | **$\overline{CE}$** | Chip Enable | Activates the device when set to Low. | | **$\overline{OE}$** | Output Enable | Gates the data to output pins during a Read. | | **$\overline{WE}$** | Write Enable | Controls the writing of data to the memory. | | **VCC/GND** | Power | Positive supply (5V) and Ground. | --- ### 4. Application Code Example To interface with the AT28HC64B using a microcontroller (like an Arduino or AVR), the logic follows a standard parallel read/write timing. ```cpp // Pseudo-code for a simple Byte Write operation void writeEEPROM(uint16_t address, uint8_t data) { digitalWrite(CHIP_ENABLE, LOW); setAddressBus(address); setDataBus(data); // Pulse Write Enable digitalWrite(WRITE_ENABLE, LOW); delayMicroseconds(1); // Small pulse width digitalWrite(WRITE_ENABLE, HIGH); digitalWrite(CHIP_ENABLE, HIGH); // Device now performs internal write cycle (max 10ms) waitForWriteCycleComplete(); } ``` ---