Cyclone II Architecture
Clock Modes
Table 2–8 summarizes the different clock modes supported by the M4K
memory.
Table 2–8. M4K Clock Modes
Clock Mode
Description
Independent In this mode, a separate clock is available for each port (ports A
and B). Clock A controls all registers on the port A side, while
clock B controls all registers on the port B side.
Input/output
Read/write
Single
On each of the two ports, A or B, one clock controls all registers
for inputs into the memory block: data input, wren, and address.
The other clock controls the block’s data output registers.
Up to two clocks are available in this mode. The write clock
controls the block’s data inputs, wraddress, and wren. The
read clock controls the data output, rdaddress, and rden.
In this mode, a single clock, together with clock enable, is used to
control all registers of the memory block. Asynchronous clear
signals for the registers are not supported.
Table 2–9 shows which clock modes are supported by all M4K blocks
when configured in the different memory modes.
Table 2–9. Cyclone II M4K Memory Clock Modes
True Dual-Port
Mode
Simple Dual-Port
Mode
Clocking Modes
Single-Port Mode
Independent
Input/output
Read/write
Single clock
v
v
v
v
v
v
v
v
M4K Routing Interface
The R4, C4, and direct link interconnects from adjacent LABs drive the
M4K block local interconnect. The M4K blocks can communicate with
LABs on either the left or right side through these row resources or with
LAB columns on either the right or left with the column resources. Up to
16 direct link input connections to the M4K block are possible from the
left adjacent LAB and another 16 possible from the right adjacent LAB.
M4K block outputs can also connect to left and right LABs through each
16 direct link interconnects. Figure 2–17 shows the M4K block to logic
array interface.
Altera Corporation
February 2007
2–31
Cyclone II Device Handbook, Volume 1
ALTERA [ ALTERA CORPORATION ]
