What exactly does EPCS and EPCQ stand for on Altera devices

[Altera_Forum]

I understand that it is something serially programmed when the FPGA is being configured, but what exactly does the acronym stand for and why is it essential in configuring the FPGA?

[Altera_Forum]

FPGAs are SRAM devices, so they need to be configured at power-on and they lose that configuration when the power goes off. 

 FPGAs can be configured from serial Flash devices or parallel Flash devices. The EPCS devices are serial Flash, also known as SPI Flash devices. I'm not sure that the characters in EPCS actually stand for anything - the S does stand for serial. An EPCQ device is a Quad-SPI flash device. If you look on the Spansion web site for their serial flash devices, you can read a data sheet there. The Altera devices are repackaged SPI Flash devices (I forget which manufacturers - but there are threads on the forum if you search it).  Cheers, Dave

[Altera_Forum]

S = Single output 

Q = Quad output

[Altera_Forum]

Back into EPC days, it stands for Enhanced Programmable Configuration device, JTAG interface with flash die. When they started to repackage SPI flash, they add 'S' into EPC so it became EPCS. Now with the Quad-SPI flash in the market, they also has EPCQ :)

[Altera_Forum]

EPCS=erasable programmable configurable serial 

Source: page1-1 of Nios II Flash Programmer User Guide.