Axcelerator Family FPGAs
v2.8
2-73
Clocks
The RCLK and the WCLK have independent source
polarity selection and can be sourced by any global or
local signal.
RAM Configurations
The AX architecture allows the read side and write side
of RAMs to be organized independently, allowing for
bus conversion. For example, the write side can be set to
256x18 and the read side to 512x9.
Both the write width and read width for the RAM blocks
can be specified independently and changed dynamically
with the WW (write width) and RW (read width) pins.
The D x W different configurations are: 128 x 36,
256 x 18, 512 x 9, 1k x 4, 2k x 2, and 4k x 1. The allowable
When widths of one, two, and four are selected, the
ninth bit is unused. For example, when writing nine-bit
values and reading four-bit values, only the first four bits
and the second four bits of each nine-bit value are
addressable for read operations. The ninth bit is not
accessible. Conversely, when writing four-bit values and
reading nine-bit values, the ninth bit of a read operation
will be undefined.
Note that the RAM blocks employ little-endian byte
order for read and write operations.
Table 2-86 RAM Signal Description
Signal
Direction
Description
WCLK
Input
Write clock (can be active on either edge).
WA[J:0]
Input
Write address bus.The value J is dependent on the RAM configuration and the number of cascaded
memory blocks. The valid range for J is from 6 to15.
WD[M-1:0]
Input
Write data bus. The value M is dependent on the RAM configuration and can be 1, 2, 4, 9, 18, or
36.
RCLK
Input
Read clock (can be active on either edge).
RA[K:0]
Input
Read address bus. The value K is dependent on the RAM configuration and the number of cascaded
memory blocks. The valid range for K is from 6 to 15.
RD[N-1:0]
Output
Read data bus. The value N is dependent on the RAM configuration and can be 1, 2, 4, 9, 18, or 36.
REN
Input
Read enable. When this signal is valid on the active edge of the clock, data at location RA will be
driven onto RD.
WEN
Input
Write enable. When this signal is valid on the active edge of the clock, WD data will be written at
location WA.
RW[2:0]
Input
Width of the read operation dataword.
WW[2:0]
Input
Width of the write operation dataword.
Pipe
Input
Sets the pipe option to be on or off.
Table 2-87 Allowable RW and WW Values
RW(2:0)
WW(2:0)
D x W
000
4k x 1
001
2k x 2
010
1k x 4
011
512 x 9
100
256 x 18
101
128 x 36
11x
reserved