DM74LS259数据手册集成电路（IC）的锁存器规格书PDF

描述 Description

General Description
These 8-bit addressable latches are designed for general purpose storage applications in digital systems. Specific uses include working registers, serial-holding registers, and active-high decoders or demultiplexers. They are multifunctional devices capable of storing single-line data in eight addressable latches, and being a 1-of-8 decoder or demultiplexer with active-high outputs.
Four distinct modes of operation are selectable by controlling the clear and enable inputs as enumerated in the function table. In the addressable-latch mode, data at the data in terminal is written into the addressed latch. The addressed latch will follow the data input with all unaddressed latches remaining in their previous states. In the memory mode, all latches remain in their previous states and are unaffected by the data or address inputs. To eliminate the possibility of entering erroneous data in the latches, the enable should be held HIGH (inactive) while the address lines are changing. In the 1-of-8 decoding or demultiplexing mode, the addressed output will follow the level of the D input with all other outputs LOW. In the clear mode, all outputs are LOW and unaffected by the address and data inputs.

特性 Features

■ 8-Bit parallel-out storage register performs serial-to-parallel
   conversion with storage
■ Asynchronous parallel clear
■ Active high decoder
■ Enable/disable input simplifies expansion
■ Direct replacement for Fairchild DM9334
■ Expandable for N-bit applications
■ Four distinct functional modes
■ Typical propagation delay times:
   Enable-to-output 18 ns
   Data-to-output 16 ns
   Address-to-output 21 ns
   Clear-to-output 17 ns
■ Fan-out
   IOL (sink current) 8 mA
   IOH (source current) −0.4 mA
■ Typical ICC 22 mA

应用 Application

■ Four distinct functional modes
■ Typical propagation delay times:
   Enable-to-output 18 ns
   Data-to-output 16 ns
   Address-to-output 21 ns
   Clear-to-output 17 ns
■ Fan-out
   IOL (sink current) 8 mA
   IOH (source current) −0.4 mA
■ Typical ICC 22 mA

简介

DM74LS259属于集成电路（IC）的锁存器。由制造生产的DM74LS259锁存器锁存器是类似于触发器的基本数字存储设备，但是不同之处在于，在锁存使能（或类似命名）信号处于有效逻辑状态的任何时间，保持的逻辑状态都可以改变。“透明”锁存器还允许设备输出在锁存使能信号有效时反映输入的当前状态，而相反的是，状态仅在保持状态已固定时改变。