Achronix Speedster22i User Macro Guide - Manual (Page 140)

Memories BRAM80KFIFO
Speedster22i Macro Cell Library Achronix Semiconductor Proprietary 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