Programmable Logic Devices: Architectures, Configuration, and Design Flow

All flashcards

What is a programmable logic device?

A PLD is an electronic component whose internal logic connections can be configured to implement a desired digital circuit function.

How does PLD programming differ from processor programming?

PLD programming configures the device's hardware logic connections. Processor programming usually changes the instructions executed by largely fixed hardware.

What are the three broad PLD categories?

In increasing order of complexity, they are simple programmable logic devices (SPLDs), complex programmable logic devices (CPLDs), and field-programmable gate arrays (FPGAs).

What is the significance of the TMS2000?

Developed by Texas Instruments in 1970 using a ROAM-based approach, it was programmed by altering a metal layer during manufacture. TI used the term programmable logic array for it.

Why is the early PLD history a shift toward user configurability?

Some early devices required factory changes to masks or metal layers. Later developments introduced erasable and field-programmable devices that gave designers more control over configuration.

Quiz questions

1. Which arrangement describes the logic arrays in a programmable logic array (PLA)?Answer: A programmable AND array feeds a programmable OR array.
2. What capability makes a generic array logic (GAL) device useful during prototyping?Answer: Its logic can be erased and reprogrammed after design changes.
3. Which logic structure is commonly used inside an FPGA?Answer: Configurable logic resources based on look-up tables.
4. What happens to the configuration of an SRAM-based PLD when power is removed?Answer: The volatile configuration is lost and must be loaded again.
5. How is a CPLD typically organized compared with a simple PAL-like device?Answer: It combines several PAL-like logic blocks linked by programmable interconnections.