EP4CE30F29C7N Datasheet, PDF (50/488 Pages) Altera Corporation – Cyclone IV Device Handbook, Volume 1

3–14
Chapter 3: Memory Blocks in Cyclone IV Devices
Clocking Modes
Clocking Modes
Cyclone IV devices M9K memory blocks support the following clocking modes:
■ Independent
■ Input or output
■ Read or write
■ Single-clock
When using read or write clock mode, if you perform a simultaneous read or write to
the same address location, the output read data is unknown. If you require the output
data to be a known value, use either single-clock mode or I/O clock mode and choose
the appropriate read-during-write behavior in the MegaWizard Plug-In Manager.
1 Violating the setup or hold time on the memory block input registers might corrupt
the memory contents. This applies to both read and write operations.
1 Asynchronous clears are available on read address registers, output registers, and
output latches only.
Table 3–5 lists the clocking mode versus memory mode support matrix.
Table 3–5. Cyclone IV Devices Memory Clock Modes
Clocking Mode
True Dual-Port
Mode
Independent
v
Input or output
v
Read or write
—
Single-clock
v
Simple
Dual-Port
Mode
—
v
v
v
Single-Port
Mode
—
v
—
v
ROM Mode FIFO Mode
v
—
v
—
—
v
v
v
Independent Clock Mode
Cyclone IV devices M9K memory blocks can implement independent clock mode for
true dual-port memories. In this mode, a separate clock is available for each port
(port A and port B). clock A controls all registers on the port A side, while clock B
controls all registers on the port B side. Each port also supports independent clock
enables for port A and B registers.
Input or Output Clock Mode
Cyclone IV devices M9K memory blocks can implement input or output clock mode
for FIFO, single-port, true, and simple dual-port memories. In this mode, an input
clock controls all input registers to the memory block including data, address,
byteena, wren, and rden registers. An output clock controls the data-output registers.
Each memory block port also supports independent clock enables for input and
output registers.
Cyclone IV Device Handbook,
Volume 1
November 2011 Altera Corporation