TriMatrix Memory
TriMatrix memory architecture can implement pipelined RAM by
registering both the input and output signals to the RAM block. All
TriMatrix memory block inputs are registered providing synchronous
write cycles. In synchronous operation, the memory block generates its
own self-timed strobe write enable (WREN) signal derived from the global
or regional clock. In contrast, a circuit using asynchronous RAM must
generate the RAM WRENsignal while ensuring its data and address
signals meet setup and hold time specifications relative to the WREN
signal. The output registers can be bypassed. Flow-through reading is
possible in the simple dual-port mode of M512 and M4K RAM blocks by
clocking the read enable and read address registers on the negative clock
edge and bypassing the output registers.
Two single-port memory blocks can be implemented in a single M4K
block as long as each of the two independent block sizes is equal to or less
than half of the M4K block size.
The Quartus II software automatically implements larger memory by
combining multiple TriMatrix memory blocks. For example, two
256 × 16-bit RAM blocks can be combined to form a 256 × 32-bit RAM
block. Memory performance does not degrade for memory blocks using
the maximum number of words available in one memory block. Logical
memory blocks using less than the maximum number of words use
physical blocks in parallel, eliminating any external control logic that
would increase delays. To create a larger high-speed memory block, the
Quartus II software automatically combines memory blocks with LE
control logic.
Clear Signals
When applied to input registers, the asynchronous clear signal for the
TriMatrix embedded memory immediately clears the input registers.
However, the output of the memory block does not show the effects until
the next clock edge. When applied to output registers, the asynchronous
clear signal clears the output registers and the effects are seen
immediately.
Parity Bit Support
The memory blocks support a parity bit for each byte. The parity bit,
along with internal LE logic, can implement parity checking for error
detection to ensure data integrity. You can also use parity-size data words
to store user-specified control bits. In the M4K and M-RAM blocks, byte
enables are also available for data input masking during write operations.
2–24
Stratix Device Handbook, Volume 1
Altera Corporation
July 2005
ALTERA [ ALTERA CORPORATION ]
