ProASIC™ 500K Family
28 v3.0
Embedded Memory Specifications
This section focuses on the embedded memory of the
ProASIC 500K family. It describes the SRAM and FIFO
interface signals and includes timing diagrams that show
the relationships of signals as they pertain to single
embedded memory blocks (Table 4 and Table 5 on page 34).
Refer to Table 3 on page 12 for basic RAM configurations.
Simultaneous Read and Write to the same location must be
done with care. On such accesses the DI bus is output to the
DO bus.
Enclosed Timing Diagrams—SRAM Mode:
•Synchronous RAM Read, Access Timed Output Strobe
(Synchronous Transparent)
•Synchronous RAM Read, Pipeline Mode Outputs
(Synchronous Pipelined)
•Asynchronous RAM Write
•Asynchronous RAM Read, Address Controlled, RDB=0
•Asynchronous RAM Read, RDB Controlled
•Synchronous RAM Write
Note: The difference between synchronous transparent
and pipeline modes is the timing of all the output
signals from the memory. In transparent mode
the outputs will change within the same clock
cycle to reflect the data requested by the currently
valid access to the memory. However, if clock
cycles are short (high clock speed), the data
requires most of the clock cycle to change to valid
values (stable signals). This makes processing of
this data in the same clock cycle nearly
impossible. Most designers solve this problem by
adding registers at all outputs of the memory to
push the data processing into the next clock cycle.
In this setup, the whole cycle time can be used to
process the data. To simplify the use of this kind of
memory setup these registers have been
implemented as part of the memory primitive
and are available to the user in the synchronous
pipeline mode. In this mode, the output signals
will change shortly after the second rising edge,
following the initiation of the read access.
Sample Macrocell Library Listing
(Worst-Case Commercial Conditions, VDDL = 2.3V, TJ = 70º C)
Cell Name Description Maximum
Intrinsic Delay Minimum
Setup/Hold Units
NAND2 2-Input NAND 0.4 ns
AND2 2-Input AND 0.4 ns
NOR3 3-Input NOR 0.4 ns
MUX2L 2-1 M ux with Active L ow Select 0.4 ns
OA21 2-Input OR into a 2-Input AND 0.4 ns
XOR2 2-Input Exclusive OR 0.3 ns
LDL Active Low Latch (LH/HL) D: 0.3/0.2 tsetup 0.5
thold 0.2 ns
DFFL Negative Edge-Triggered D-type Flip-Flop (LH/HL) CLK-Q:
0.4/0.4 tsetup 0.4
thold 0.2 ns
Note: Assumes fanout of two.
Table 4 •Memory Block SRAM Interface Signals
SRAM Signal Bits In/Out Description
WCLKS 1 IN Write clock used on synchronization on write side
RCLKS 1 IN Read clock used on synchronization on read side
RADDR<0:7> 8 IN Read address
RBLKB 1 IN Negative true read block select
RDB 1 IN Negative true read pulse
WADDR<0:7> 8 IN Write address
WBLKB 1 IN Negative true write block select
DI<0:8> 9 IN Input data bits <0:8>, <8> can be used for parity in
WRB 1 IN Negative true write pulse
DO<0:8> 9 OUT Output data bits <0:8>, <8> can be used for parity out
RPE 1 OUT Read parity error
WPE 1 OUT Write parity error
PARODD 1 IN S elects odd parity generation/detect when high, even when low
Note: Not all signals shown are used in all modes.