EP4SE360F35I4 Datasheet, PDF (75/432 Pages) Altera Corporation – This section provides a complete overview of all features relating to the Stratix IV device family, which is the most architecturlly advanced

Chapter 3: TriMatrix Embedded Memory Blocks in Stratix IV Devices
Design Considerations
3–19
MLABs can implement single-port SRAM through emulation using the Quartus II
software. Emulation results in minimal additional logic resources being used. Because
of the dual-purpose architecture of the MLAB, it only has data input registers and
output registers in the block. MLABs gain input address registers and additional data
output registers from ALMs.
f For more information about register packing, refer to the Logic Array Blocks and
Adaptive Logic Modules in Stratix IV Devices chapter.
Conflict Resolution
When using memory blocks in true dual-port mode, it is possible to attempt two write
operations to the same memory location (address). Because no conflict resolution
circuitry is built into the memory blocks, this results in unknown data being written to
that location. Therefore, you must implement conflict resolution logic external to the
memory block to avoid address conflicts.
Read-During-Write Behavior
You can customize the read-during-write behavior of the Stratix IV TriMatrix memory
blocks to suit your design needs. Two types of read-during-write operations are
available: same port and mixed port. Figure 3–15 shows the difference between the
two types.
Figure 3–15. Stratix IV Read-During-Write Data Flow
Port A
data in
Port A
data out
Port B
data in
Port B
data out
Mixed-port
data flow
Same-port
data flow
Same-Port Read-During-Write Mode
This mode applies to either a single-port RAM or the same port of a true dual-port
RAM. For MLABs, the output of the MLABs can only be set to don’t care in same-port
read-during-write mode. In this mode, the output of the MLABs is unknown during a
write cycle. There is a window near the falling edge of the clock during which the
output is unknown. Prior to that window, “old data” is read out; after that window,
“new data” is seen at the output.
December 2011 Altera Corporation
Stratix IV Device Handbook
Volume 1