programmable gate array

Thread Starter

PG1995

Joined Apr 15, 2011
818
Hi

I didn't know there existed programmable gate array. If I have a programmable chip, then can I configure it to behave, say, like the 74LS00 IC? What device is used to program the gate array? Is there something like USB SD card reader? Please help me with this query. Thanks.
 

kubeek

Joined Sep 20, 2005
5,732
Well, yes you can create a quadruple nand gate, but definitely not in the same package and with the same pinout.
FPGAs I know need some form of external memory, because the chip remembers nothing and needs to be programmed each time you power it up.
On the contrary, CPLDs do remember their programming. Read here and here.
 

kubeek

Joined Sep 20, 2005
5,732
Like microcontrollers, each brand will have its own programming cable. Xilinx uses JTAG protocol, not sure about altera but I bet they will use something different.
 

Thread Starter

PG1995

Joined Apr 15, 2011
818
Thank you, Kubeek, Colin.

Now I wonder why would someone buy regular IC such as 74LS00 instead of a programmable chip which can be configured to emulate behaviour of different logic chips? To me, programmable one is a many-in-one device and even if it costs slightly higher even then it's worth it. Thanks.
 

crutschow

Joined Mar 14, 2008
25,377
Programmable chips are often used to implement large, complex logic functions. They wouldn't be use to replace simple logic chips like the 74LS00 since they are significantly physically larger, need to be programmed, and cost much more than the simple chips.
 
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