Altera Cyclone IV - Address Clock Enable Support

Chapter 3: Memory Blocks in Cyclone IV Devices 3–5
Overview
November 2011 Altera Corporation Cyclone IV Device Handbook,
Volume 1
Address Clock Enable Support
Cyclone IV devices M9K memory blocks support an active-low address clock enable,
which holds the previous address value for as long as the
addressstall signal is high
(
addressstall = '1' ). When you configure M9K memory blocks in dual-port mode,
each port has its own independent address clock enable.
Figure 3–2 shows an address clock enable block diagram. The address register output
feeds back to its input using a multiplexer. The multiplexer output is selected by the
address clock enable (
addressstall ) signal.
The address clock enable is typically used to improve the effectiveness of cache
memory applications during a cache-miss. The default value for the address clock
enable signals is low.
Figure 3–2. Cyclone IV Devices Address Clock Enable Block Diagram
address[0]
address[N]
addressstall
clock
address[0]
register
address[N]
register
address[N]
address[0]