How do you replace obsolete 74 series glue logic?
You take the original design and implement it in a newer programmable logic device, then build and test the parts to prove they behave like the originals. The 74 series was the backbone of old digital design, and boards that relied heavily on glue logic were exposed when those parts went out of production. Force Technologies founder Mike Salmon was closely involved in this work, and describes it as one of the areas that brought the company a lot of business.
He tells the fuller story in Force Tech Talk 24, our founder-story conversation with Mike Salmon.
What are the steps?
| Step | What happens | Why it matters |
|---|---|---|
| 1. Take the old design | The original obsolete logic is captured as a design | The customer’s qualified board stays unchanged |
| 2. Implement it in a new device | The design is built into a programmable logic device | One device can replace several of the old parts |
| 3. Build the parts | The new devices are manufactured | The customer receives a usable component |
| 4. Test and prove | Each part is tested against what the original was supposed to do | The replacement is shown to work, not assumed |
Why can one new device replace four old ones?
Because the old logic was quite simple, and a single programmable device has room to carry the function of several of them. Mike’s point is that the new technology could do the job of four of the old parts, which in his words made the result better.
When is this the right route?
It suits boards where the logic parts are obsolete but the rest of the design is still sound. If the original die survives, re-manufacture is an option, and where nothing survives a form fit function replacement can be designed. Force engineers help work out which applies.
Force Technologies has supplied, tested, re-manufactured and stored obsolete semiconductors since 1986, from our UK facility in Wiltshire, certified to AS9100 Rev D.
Frequently asked questions
How do you replace obsolete 74 series glue logic?
The original design is implemented in a newer programmable logic device, then the parts are built and tested to prove they do what the originals were supposed to do.
Can one programmable device replace several old logic parts?
Yes. In Force Technologies’ experience a single programmable device could do the job of four of the old, simple logic parts.