EP3C16F256I7N Altera, EP3C16F256I7N Datasheet - Page 69

• Manufacturer Part Number: EP3C16F256I7N
• Description: Cyclone III
• Manufacturer: Altera

Figure 4–12. Cyclone III True Dual-Port Timing Waveforms
Altera Corporation-Preliminary
March 2007
q_a (asynch)
q_b (asynch)
address_a
address_b
data_a
rden_a
wren_a
wren_b
rden_b
clk_a
clk_b
din-1
an-1
doutn-1
bn
din-1
din
In true dual-port mode, you can access any memory location at any time
from either port A or port B. When accessing the same memory location
from both ports, you must avoid possible write conflicts. A write conflict
happens when you attempt to write to the same address location from
both ports at the same time. This will result in unknown data being stored
to that address location. There is no conflict resolution circuitry built into
the Cyclone III M9K memory blocks. You must handle address conflicts
external to the RAM block.
Figure 4–12
operation at port A and read operation at port B. Registering the RAM's
outputs would simply delay the q outputs by one clock cycle.
Shift Register Mode
Cyclone III memory blocks can implement shift registers for digital signal
processing (DSP) applications, such as finite impulse response (FIR)
filters, pseudo-random number generators, multi-channel filtering, and
auto-correlation and cross-correlation functions. These and other DSP
applications require local data storage, traditionally implemented with
standard flip-flops that quickly exhaust many logic cells for large shift
registers. A more efficient alternative is to use embedded memory as a
shift register block, which saves logic cell and routing resources.
The size of a (w x m x n) shift register is determined by the input data
width (w), the length of the taps (m), and the number of taps (n), and must
be less than or equal to the maximum number of memory bits, which is
an
doutn
din
b0
a0
shows true dual-port timing waveforms for the write
dout0
a1
dout0
dout1
b1
a2
dout2
Cyclone III Device Handbook, Volume 1
a3
dout3
dout1
b2
din4
a4
din4
din5
a5
Memory Modes
dout2
din5
b3
din6
a6
4–15