DM74ALS646WM

Overview

The DM74ALS646WM is an octal 3-STATE bus transceiver and register manufactured by onsemi. It features totem-pole outputs designed for driving highly-capacitive or low-impedance loads, enabling direct connection to bus lines without interface components. The device incorporates independent edge-triggered D-type flip-flops for buses A and B, controlled by CAB and CBA clock inputs. Select pins SAB and SBA allow switching between real-time data transfer and stored data output using a make-before-break configuration to prevent glitches. The G and DIR control pins provide four operational modes including bidirectional data transfer and internal storage.

Feature Summary

• Octal 3-STATE bus transceiver with dedicated registers for multiplexed transmission
• Totem-pole outputs capable of driving high-capacitance loads directly
• Independent D-type registers for Bus A and Bus B with glitch-free selection
• Four-mode operation controlled by enable and direction signals

Applications

• Buffer registers in bus-organized systems
• Bidirectional bus drivers
• I/O ports
• Working registers

Procurement Notes

Verify the manufacturer origin as Fairchild Semiconductor legacy products are now managed by onsemi. Confirm the package type corresponds to the M24B designation for the 24-Lead Small Outline Integrated Circuit (SOIC). Ensure compatibility with the Advanced oxide-isolated, ion-implanted Schottky TTL process specifications required for the application environment.

Selection Notes

Select this component when an octal transceiver with integrated storage is required for bidirectional data flow. The device supports both real-time and stored data paths via specific select pins. Verify that the operating voltage range of 4.5V to 5.5V aligns with the system power supply. Consider the 3-STATE output capability for direct bus interfacing without additional pull-up components.

Part Context

This part belongs to the 74ALS logic family, utilizing an advanced oxide-isolated, ion-implanted Schottky TTL process. It combines the functionality of a bus transceiver with dual octal D-type registers. The device is available in a 24-Lead SOIC package (M24B) and supports switching specifications at 50 pF load conditions across the full temperature range.

Replacement Considerations

Check for equivalent parts from other manufacturers within the 74ALS series that offer identical pinouts and electrical characteristics. Verify if alternative packages such as PDIP are acceptable substitutes if the SOIC form factor is not strictly required.