Altera First-In-First-Out Partitioner - Manual (Page 17)

Altera Corporation 15
Getting Started FIFO Partitioner Megafunction User Guide
Figure 9. Writing 16-bit words and reading 8-bit words
FIFOs with a narrow write port and a wide read port
Figure 10 illustrates write and read operations to a FIFO with a 8-bit-wide
write-side bus, and a 16-bit-wide read-side bus. In this example the read
port is operating at half the frequency of the write port. Four 8-bit words
are written to the FIFO. Notice that the wr_level_3 flag is incremented
to 4, and the rd_level_3 flag is incremented to 2. Two 16-bit word read
operations empty the FIFO. Notice that the first 8-bits written to the FIFO
are the least-significant 8 bits in the 16-bit read operation. Also note that
rd_empty_n
does not deassert, indicating that data is available, until
enough words have been written on the narrow write port, to fill an entire
word on the wide read-side port.
clk_port_a_2
wr_en_a_2
wr_data_a_2
wr_level_2
wr_empty_2
wr_full_2
clk_port_b_2
read_b_2
rd_data_b_2
rd_level_2
rd_full_2
rd_empty_2
1 0
00
0 2 4 3 2 1 0
00 02 01 FF
2 1
FF01 0002 0003 0004 0005 0007 0006 0008