This monolithic quadruple two-input multiplexer with storage provides essentially the equivalent functional capabilities of two separate MSI functions (SN54LS157/SN74LS157 and SN54LS175/SN74LS175) in a single 16-pin package.

When the word-select input is low, word 1 (A1, B1, C1, D1) is applied to the flip-flops. A high input to word select will cause the selection of word 2 (A2, B2, C2, D2). The selected word is clocked to the output terminals on the positive-going edge of the clock pulse.

Typical power dissipation is 37 milliwatts. The SN54LS399 is characterized for operation over the full military range of -55°C to 125°C. The SN74LS399 is characterized for operation from 0°C to 70°C.

• Single-Rail Outputs on 'LS399
• Selects One of Two 4-Bit Data Sources and Stores Data Synchronously with System Clock
• Applications:
  • Dual Source for Operands and Constants in Arithmetic Processor; Can Release Processor Register Files for Acquiring New Data
  • Implement Separate Registers Capable of Parallel Exchange of Contents Yet Retain External Load Capability
  • Universal Type Register for Implementing Various Shift Patterns: Even Has Compound Left-Right Capabilities

• Technology Family
• LS
• Function
• Digital Multiplexer
• Configuration
• 8:4, 2:1
• Number of channels (#)
• 4
• Operating temperature range (C)
• 0 to 70
• Rating
• Catalog

SN74LS399的完整型号有：SN74LS399N，以下是这些产品的关键参数及官网采购报价：

SN74LS399N，工作温度：0 to 70，封装：PDIP (N)-16，包装数量MPQ：25个，MSL 等级/回流焊峰值温度：N/A for Pkg Type，引脚镀层/焊球材料：NIPDAU，TI官网SN74LS399N的批量USD价格：.844（1000+）

14-24-LOGIC-EVM — 支持 14 到 24 引脚 PW、DB、D、DW、NS、DYY 和 DGV 封装的通用逻辑 EVM

该 EVM 设计用于支持采用 14 至 24 引脚 D、DW、DB、NS、PW、DYY 或 DGV 封装的任何逻辑器件。