## HCS166HMSR Overview The **HCS166HMSR** is a high-performance, radiation-hardened (Rad-Hard) 8-bit parallel-in/serial-out shift register. It belongs to the **Space Electronics** category, specifically designed for military and aerospace applications where reliability in extreme radiation environments is mandatory. --- ### 1. Key Technical Specifications The HCS166HMSR is part of the CMOS family and is designed to operate under harsh conditions. | Parameter | Specification | | :--- | :--- | | **Logic Type** | 8-Bit Shift Register (Parallel-In, Serial-Out) | | **Technology** | Radiation Hardened CMOS | | **Operating Voltage ($V_{CC}$)** | 4.5V to 5.5V | | **Radiation Tolerance (Total Dose)** | $1 \times 10^5$ RAD (Si) | | **Package Type** | Ceramic Dual-In-Line (CDIP) or Flatpack | | **Operating Temperature Range** | -55°C to +125°C | --- ### 2. Functional Description The device consists of eight flip-flops with a common clock and a control system. It provides the following functionalities: * **Synchronous Parallel Load:** When the Shift/Load ($SH/\overline{LD}$) input is Low, data is loaded into the register from the parallel inputs ($P_0$ to $P_7$) on the next positive clock transition. * **Serial Shifting:** When $SH/\overline{LD}$ is High, data shifts one bit toward the serial output ($Q_7$) on each positive clock edge. * **Clock Inhibit:** A clock inhibit ($\overline{CLK\ INH}$) input allows the user to freeze the current state of the register regardless of the clock signal. * **Direct Clear:** An overriding asynchronous Master Reset ($\overline{MR}$) is provided to clear all flip-flops to a Low state. --- ### 3. Pin Configuration and Logic The device typically features 16 pins. The core logic pins are defined below: | Pin Name | Function | Description | | :--- | :--- | :--- | | **CP** | Clock Pulse | Triggers shifting or loading on the rising edge. | | **$P_0 - P_7$** | Parallel Inputs | Data inputs for parallel loading. | | **$Q_7$** | Serial Output | The output of the last stage in the shift register. | | **$DS$** | Serial Input | Input for serial data during shifting. | | **$\overline{MR}$** | Master Reset | Asynchronous active-low reset. | | **$SH/\overline{LD}$** | Shift/Load | Controls whether the device shifts or loads parallel data. | --- ### 4. Radiation Hardness Features The "HSR" suffix indicates specific screening and hardening processes: 1. **Latch-Up Immunity:** The device is immune to Single Event Latch-up (SEL) due to its specialized Silicon-on-Sapphire (SOS) or bulk CMOS epitaxial processes. 2. **SEU Resistance:** Design techniques are employed to minimize Single Event Upset (SEU) rates in high-energy particle environments. 3. **Screening:** Tested according to MIL-STD-883 methods, ensuring suitability for satellites and deep-space probes.