Chapter 3: Memory Blocks in Arria II Devices
3–17
Memory Modes
December 2010
Altera Corporation
Arria II Device Handbook Volume 1: Device Interfaces and Integration
shows true dual-port timing waveforms for the write operation at port A
and the read operation at port B with the read-during-write behavior set to
new data
.
Registering the RAM outputs delay the
q
outputs by one clock cycle.
Shift-Register Mode
All Arria II memory blocks support shift register mode. Embedded memory block
configurations 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- and cross-correlation functions. These
and other DSP applications require local data storage, traditionally implemented with
standard flipflops 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 shift register (
w
×
m
×
n
) is determined by the input data width (
w
), the
length of the taps (
m
), and the number of taps (
n
). You can cascade memory blocks to
implement larger shift registers.
Figure 3–17. True Dual-Port Timing Waveform
clk_a
wren_a
address_a
clk_b
an-1
an
a0
a1
a2
a3
a4
a5
a6
q_b (asynch)
wren_b
address_b
bn
b0
b1
b2
b3
doutn-1
doutn
dout0
q_a (asynch)
din-1
din
din4
din5
din6
data_a
din-1
din
dout0
dout1
dout2
dout3
din4
din5
dout2
dout1