74HC259D/74HCT259D是8位可尋址鎖存器介紹：

The 74HC/HCT259 are high-speed Si-gate CMOS devices and are pin compatible with low power Schottky TTL (LSTTL). They are specified in compliance with JEDEC standard no. 7A.

The 74HC/HCT259 are high-speed 8-bit addressable latches designed for general purpose storage applications in digital systems. The “259” are multifunctional devices capable of storing single-line data in eight addressable latches, and also 3-to-8 decoder and demultiplexer, with active HIGH outputs (Q0 to Q7), functions are available.

The “259” also incorporates an active LOW common reset (MR) for resetting all latches, as well as, an active LOW enable input (LE).

The “259” has four modes of operation as shown in the mode select table. In the addressable latch mode, data on the data line (D) is written into the addressed latch. The

addressed latch will follow the data input with all non-addressed 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. In the 3-to-8 decoding or demultiplexing mode, the addressed output follows the state of the D input with all other outputs in the LOW state. In the reset mode all outputs are LOW and unaffected by the address (A0 to A2) and data (D) input. When operating the “259” as an addressable latch, changing more than one bit of address could impose a transient-wrong address. Therefore, this should only be done while in the memory mode. The mode select table summarizes the operations of the “259”.

74HC259D/74HCT259D功能說明
· Combines demultiplexer and 8-bit latch
· Serial-to-parallel capability
· Output from each storage bit available
· Random (addressable) data entry
· Easily expandable
· Common reset input
· Useful as a 3-to-8 active HIGH decoder
· Output capability: standard
· ICC category: MSI

74HC259D/74HCT259D引腳管腳說明-PIN DESCRIPTION
PIN NO. SYMBOL NAME AND FUNCTION
1, 2, 3 A0 to A2 address inputs
4, 5, 6, 7, 9 10, 11, 12 Q0 to Q7 latch outputs
8 GND ground (0 V)
13 D data input
14 LE latch enable input (active LOW)
15 MR conditional reset input (active LOW)
16 VCC positive supply voltage

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