4-by-4 register files with 3-state outputs


Product details


Technology Family LS VCC (Min) (V) 4.75 VCC (Max) (V) 5.25 Bits (#) 16 Voltage (Nom) (V) 5 F @ nom voltage (Max) (MHz) 35 ICC @ nom voltage (Max) (mA) 50 Propagation delay (Max) (ns) 50 IOL (Max) (mA) 8 IOH (Max) (mA) -2.6 3-state output Yes Operating temperature range (C) 0 to 70 open-in-new Find other Other latch

Package | Pins | Size

PDIP (N) 16 181 mm² 19.3 x 9.4 SOIC (D) 16 59 mm² 9.9 x 6 SOP (NS) 16 80 mm² 10.2 x 7.8 open-in-new Find other Other latch


  • Separate Read/Write Addressing Permits Simultaneous Reading and Writing
  • Fast Access Times…Typically 20 ns
  • Organized as 4 Words of 4 Bits
  • Expandable to 512 Words of n-Bits
  • For Use as:
    • Scratch-Pad Memory
    • Buffer Storage between Processors
    • Bit Storage in Fast Multiplication Designs
  • 3-State Outputs
  • SN54LS170 and SN74LS170 Are Similar But Have Open-Collector Outputs


open-in-new Find other Other latch


The SN54LS670 and SN74LS670 MSI 16-bit TTL register files incorporate the equivalent of 98 gates. The register file is organized as 4 words of 4 bits each and separate on-chip decoding is provided for addressing the four word locations to either write-in or retrieve data. This permits simultaneous writing into one location and reading from another word location.

Four data inputs are available which are used to supply the 4-bit word to be stored. Location of the word is determined by the write-address inputs A and B in conjunction with a write-enable signal. Data applied at the inputs should be in its true form. That is, if a high-level signal is desired from the output, a high-level is applied at the data input for that particular bit location. The latch inputs are arranged so that new data will be accepted only if both internal address gate inputs are high. When this condition exists, data at the D input is transferred to the latch output. When the write-enable input, G\W, is high, the data inputs are inhibited and their levels can cause no change in the information stored in the internal latches. When the read-enable input, G\R, is high, the data outputs are inhibited and go into the high-impedance state.

The individual address lines permit direct acquisition of data stored in any four of the latches. Four individual decoding gates are used to complete the address for reading a word. When the read address is made in conjunction with the read-enable signal, the word appears at the four outputs.

This arrangement — data-entry addressing separate from data-read addressing and individual sense line — eliminates recovery times, permits simultaneous reading and writing, and is limited in speed only by the write time (27 nanoseconds typical) and the read time (24 nanoseconds typical). The register file has a nondestructive readout in that data is not lost when addressed.

All inputs except read enable and write enable are buffered to lower the drive requirements to one Series 54LS/74LS standard load, and input-clamping diodes minimize switching transients to simplify system design. High-speed, double-ended AND-OR-INVERT gates are employed for the read-address function and have high-sink-current, three-state outputs. Up to 128 of these outputs may be bus connected for increasing the capacity up to 512 words. Any number of these registers may be paralleled to provide n-bit word length.

The SN54LS670 is characterized for operation over the full military temperature range of -55°C to 125°C; the SN74LS670 is characterized for operation from 0°C to 70°C.


open-in-new Find other Other latch

Technical documentation

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Type Title Date
* Datasheet 4-by-4 Register Files With 3-State Outputs datasheet Mar. 01, 1988
Selection guides Logic Guide (Rev. AB) Jun. 12, 2017
Application notes Understanding and Interpreting Standard-Logic Data Sheets (Rev. C) Dec. 02, 2015
Application notes Power-Up Behavior of Clocked Devices (Rev. A) Feb. 06, 2015
User guides LOGIC Pocket Data Book (Rev. B) Jan. 16, 2007
Application notes Semiconductor Packing Material Electrostatic Discharge (ESD) Protection Jul. 08, 2004
More literature Logic Cross-Reference (Rev. A) Oct. 07, 2003
Application notes TI IBIS File Creation, Validation, and Distribution Processes Aug. 29, 2002
Application notes Designing With Logic (Rev. C) Jun. 01, 1997
Application notes Designing with the SN54/74LS123 (Rev. A) Mar. 01, 1997
Application notes Input and Output Characteristics of Digital Integrated Circuits Oct. 01, 1996
Application notes Live Insertion Oct. 01, 1996

Design & development

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Hardware development

document-generic User guide
This EVM is designed to support any logic device that has a D, DW, DB, NS, PW, P, N, or DGV package in a 14 to 24 pin count.
  • Board design allows for versatility in evaluation
  • Supports a wide-range of logic devices

CAD/CAE symbols

Package Pins Download
PDIP (N) 16 View options
SO (NS) 16 View options
SOIC (D) 16 View options

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