A filter, in particular, a finite impulse response (FIR) filter having a
variable data input and output rate is disclosed. The FIR filter includes
a first-in first-out (FIFO) architectural buffer, an address generator
for circularly generating respective addresses for FIFO of data items and
providing the addresses to the buffer, a filter for performing filtering
on data items having different rates, which are input from the buffer,
and outputting one or more data, and a controller for controlling address
generation of the address generator and controlling transfer paths of
data items for filtering of the filter. It is possible to variably
control the input and output rate of filtering data by the FIR filter.