FIFO Memory

parity check.......

Parity.

Because the user (or application) needs 9 bits. Perhaps for parity. I know of instruments need 9, 10 or perhaps 12 bits of data. No need to have extra ICs in that memory.

gm

Parity bit, or extra bit to differentiate between control and data... whatever the application may seem fit.

But as there are a lot of applications using that extra bit, chip manufacturers have thoguht sensibly tthat it was better to support only 9 bit multiples as 8 bit multiples are included, and not the other way round...

regards

I think there's also a couple historical reasons. Back in the good ole days, 9-track tape drives needed a fifo for deskewing the data. So the fifos all had a width of nine bits so they could be used for that application.

Also Sony, in the 80's, felt that the lowest number of bits needed to do a straight capture of broadcast quality analog video was nine. I'm guessing that this created at least a small market for fifo chips in time base correctors and the like.

It can be for defining the DL/UL direction, Control/Status Register , R/W Operation, Parity Bit.

Karthik Balaguru