The **MSM586SEN** is a specialized Integrated Circuit (IC) produced by **OKI Electric Industry** (now part of ROHM Semiconductor). It is primarily known as a **Real-Time Clock (RTC)** and **Calendar** chip, commonly used in early computing systems and embedded devices to maintain time. --- ## 1. Technical Specifications Below are the primary electronic characteristics of the MSM586SEN: | Feature | Specification | | :--- | :--- | | **Type** | Real-Time Clock / Calendar | | **Interface** | Parallel (Bus-oriented) | | **Supply Voltage (Vcc)** | 2.0V to 6.0V (Typical 5V) | | **Package Type** | 18-pin DIP (Dual In-line Package) | | **Clock Input** | 32.768 kHz Crystal Oscillator | | **Logic** | CMOS Low Power Technology | --- ## 2. Key Internal Components The chip is divided into several functional blocks that manage timekeeping and data transfer: ### A. Oscillator Circuit The IC contains an internal inverter for use with an external **32.768 kHz** crystal. This frequency is standard because it can be divided by $2^{15}$ to produce exactly one pulse per second. ### B. Register Map The MSM586SEN stores time data in BCD (Binary Coded Decimal) format. It tracks: * Seconds, Minutes, Hours * Day of the week * Day of the month, Month, Year * Leap year compensation ### C. Bus Interface It features an asynchronous bus interface, meaning it communicates with a CPU using standard `RD` (Read), `WR` (Write), and `CS` (Chip Select) signals. It acts as a peripheral mapped into the memory or I/O space of the processor. --- ## 3. Pin Configuration (18-pin DIP) While specific pinouts should always be verified against the official datasheet, the general layout includes: 1. **Vcc / GND:** Power supply pins. 2. **XT / XT-bar:** Connections for the 32.768 kHz crystal. 3. **D0 - D3:** 4-bit Data Bus (common in older 4-bit or 8-bit systems). 4. **A0 - A3:** Address lines to select which time register to read/write. 5. **Control Lines:** `CS` (Chip Select), `RD` (Read), `WR` (Write). --- ## 4. Operational Features * **Low Power Consumption:** Designed to run off a small battery (like a CR2032) when the main system power is turned off. * **12/24 Hour Format:** Can be toggled between standard or military time formats. * **Interrupt Outputs:** Can often be programmed to send a signal to the CPU at specific intervals (1 second, 1 minute, etc.). --- ## 5. Typical Application Circuit ```c // Pseudo-logic for reading the clock 1. Set CS (Chip Select) to LOW. 2. Place the Address of the "Seconds" register on A0-A3. 3. Set RD (Read) to LOW. 4. Read BCD data from D0-D3. 5. Set RD and CS back to HIGH. ```