8−Stage Shift/Store Register with Three−State Outputs # Technical Documentation: MC14094BCPG 8-Stage Shift-and-Store Register
Manufacturer : ON Semiconductor
Component Type : CMOS 8-Stage Serial Shift/Parallel Storage Register
Package : PDIP-16 (C Package)
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## 1. Application Scenarios
### Typical Use Cases
The MC14094BCPG is a versatile CMOS integrated circuit primarily functioning as an 8-bit serial-in, parallel-out shift register with output latches . Its core operation involves shifting serial data through its internal stages on clock edges and then transferring that data to parallel output latches upon a separate strobe command.
Primary Operational Modes:
* Serial-to-Parallel Data Conversion: Converts a single stream of serial data (on the `DATA` pin) into 8 parallel bits (`Q1` to `Q8`). This is fundamental for interfacing serial communication lines (e.g., from a microcontroller's SPI or a software-based bit-bang serial port) to multiple parallel outputs.
* Output Expansion: A single microcontroller GPIO pin can control up to 8 output lines by daisy-chaining multiple MC14094s. Data is shifted through the chain, and a common strobe signal latches the data to all outputs simultaneously, minimizing processor I/O requirements.
* LED Matrix or Display Driver: Efficiently drives rows or columns of LED matrices, 7-segment displays, or other multi-element visual indicators by serially loading the desired pattern.
* Remote Latching Output Buffer: The internal storage latches allow the shift register to be loaded with new data while the outputs remain stable, holding their previous state. The new data appears on the outputs only when the `STROBE` pin is activated, enabling synchronized updates across multiple devices or systems.
### Industry Applications
* Industrial Control Systems: Used in PLCs (Programmable Logic Controllers) and control panels to expand digital output channels for driving relays, solenoids, and indicator lamps.
* Consumer Electronics: Found in appliances, audio equipment, and older display systems for front-panel control and status indication.
* Automotive Electronics: Employed in non-critical body control modules for functions like lighting control (e.g., sequential turn signals) and switch matrix scanning, where its wide supply voltage range is beneficial.
* Test and Measurement Equipment: Utilized to set digital states on multiple test points or to control multiplexers and signal routing switches.
* Retro Computing & Hobbyist Projects: A staple in digital logic and microcontroller projects for I/O expansion due to its simplicity and robustness.
### Practical Advantages and Limitations
Advantages:
* High Noise Immunity: CMOS technology provides excellent noise margins, typically 45% of the supply voltage (`VDD`).
* Wide Operating Voltage Range: Can operate from 3.0V to 18V , making it compatible with 5V TTL, 3.3V CMOS, and higher voltage systems.
* Low Power Consumption: Features very low static power dissipation (in the nanoampere range for quiescent current), ideal for battery-sensitive applications.
* High Output Drive Capability: Can sink/source significant current (e.g., can drive up to 10 LSTTL loads directly).
* Three-State Outputs: The `Q8` serial output and the parallel outputs (`Q1-Q8`) can be put into a high-impedance state using the `OUTPUT ENABLE` pin, facilitating bus-oriented designs.
Limitations:
* Moderate Speed: Maximum clock frequency is typically 8 MHz at 10V `VDD` (lower at reduced voltage). Not suitable for high-speed serial data links.
* Latch-Up Risk: Early CMOS devices are susceptible to latch-up if input signals exceed the supply
