Achronix Speedster22i User Macro Guide User Manual
Page 140
Memories
BRAM80KFIFO
Speedster22i Macro Cell Library
PAGE 123
Table 6-19: FIFO read_width versus Maximum Read Depth
read_width
FIFO Read
Depth
fwft = 1’b0
FIFO Read
Depth
fwft = 1’b1
40
2048
2049
36
2048
2049
32
2048
2049
20
4096
4097
18
4096
4097
16
4096
4097
10
8192
8193
9
8192
8193
8
8192
8193
5
16384
16385
4
16384
16385
2
32768
32769
1
65536
65537
Table 6-20: dout bit assignments per read_width values
read_width
doutpx[3:0]
doutp[3:0]
dout[31:0]
user_dout[39:36]
user_dout[35:32]
user_dout[31:0]
4’hx
user_dout[35:32]
user_dout[31:0]
4’hx
4’hx
user_dout[31:0]
2’bxx,user_dout[19:18]
2’bxx,user_dout[17:16]
16’hxxxx,user_dout[15:0]
4’hx
user_dout[17:16]
16’hxxxx,user_dout[15:0]
4’hx
4’hx
16’hxxxx,user_dout[15:0]
3’bxxx,user_dout[9]
3’bxxx,user_dout[8]
24’hxxxxxx,user_dout[7:0]
4’hx
3’bxxx,user_dout[8]
24’hxxxxxx,user_dout[7:0]
4’hx
4’hx
24’hxxxxxx,user_dout[7:0]
4’hx
3’bxxx,user_dout[4]
28’hxxxxxxx,user_dout[3:0]
4’hx
4’hx
28’hxxxxxxx,user_dout[3:0]
4’hx
4’hx
30’hxxxxxxxx,user_dout[1:0]
4’hx
4’hx
31’hxxxxxxxx,user_dout[0]
Required Relationship of write_width to read_width parameter assignments
The BRAM80KFIFO block supports memory widths from one to forty bits wide. The width of
the din data input is determined by the write_width parameter while the width of the dout
data output is determined by the read_width parameter. The width of read port may be set to
be different from the width of the write port. There are, however, some limitations of the port
width assignments between the read and write width assignments. The valid port widths
defined in
Table 6‐16: BRAM80KFIFO Parameters
may be divided into three groups:
•
Group1 (n x 5 widths): 40, 20, 10, 5
•
Group2 (n x 9 widths): 36, 18, 9
•
Group3 (2
n
widths): 32, 16, 8, 4, 2, 1
40
36
32
20
18
16
10
9
8
5
4
2
1