SRAM and FIFO Memories in Actel’s Low-Power Flash Devices
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SRAM Features
RAM4K9 Macro
RAM4K9 is the dual-port configuration of the RAM block (
Figure 6-4). The RAM4K9 nomenclature
refers to both the deepest possible configuration and the widest possible configuration the dual-
port RAM block can assume, and does not denote a possible memory aspect ratio. The RAM block
can be configured to the following aspect ratios: 4,096x1, 2,048x2, 1,024x4, and 512x9. RAM4K9 is
fully synchronous and has the following features:
Two ports that allow fully independent reads and writes at different frequencies
Selectable pipelined or nonpipelined read
Active-low block enables for each port
Toggle control between read and write mode for each port
Active-low asynchronous reset
Pass-through write data or hold existing data on output. In pass-through mode, the data
written to the write port will immediately appear on the read port.
Designer software will automatically facilitate falling-edge clocks by bubble-pushing the
inversion to previous stages.
Signal Descriptions for RAM4K9
Note: Automotive ProASIC3 devices support single-port SRAM capabilities, or dual-port SRAM only
under specific conditions. Dual-port mode is supported if the clocks to the two SRAM ports
are the same and 180° out of phase (i.e., the port A clock is the inverse of the port B clock).
Since Actel Libero IDE macro libraries support a dual-port macro only, certain modifications
must be made. These are detailed below.
The following signals are used to configure the RAM4K9 memory element:
WIDTHA and WIDTHB
These signals enable the RAM to be configured in one of four allowable aspect ratios
(Table 6-2 onNote: When using the SRAM in single-port mode for Automotive ProASIC3 devices, WIDTHB should
be tied to ground.
Note: For timing diagrams of the RAM signals, refer to the appropriate family datasheet.
Figure 6-4 RAM4K9 Simplified Configuration
DINA
DOUTA
DOUTB
Write Data
RAM4K9
Reset
Write Data
Read Data
DINB
ADDRA
Address
ADDRB
BLKA
BLK
BLKB
WENA
WEN
WENB
CLKA
CLK
CLKB