DDR for Actel’s Low-Power Flash Devices
9- 14
v1.1
module ddr_test(DIN, CLK, CLR, DOUT);
input
DIN, CLK, CLR;
output DOUT;
Inbuf_ddr Inbuf_ddr (.PAD(DIN), .CLR(clr), .CLK(clk), .QR(qr), .QF(qf));
Outbuf_ddr Outbuf_ddr (.DataR(qr),.DataF(qf), .CLR(clr), .CLK(clk),.PAD(DOUT));
INBUF INBUF_CLR (.PAD(CLR), .Y(clr));
INBUF INBUF_CLK (.PAD(CLK), .Y(clk));
endmodule
Simulation Consideration
Actel DDR simulation models use inertial delay modeling by default (versus transport delay
modeling). As such, pulses that are shorter than the actual gate delays should be avoided, as they
will not be seen by the simulator and may be an issue in post-routed simulations. The user must be
aware of the default delay modeling and must set the correct delay model in the simulator as
needed.
Conclusion
IGLOO, Fusion, and ProASIC3 devices support a wide range of DDR applications with different I/O
standards and include built-in DDR macros. The powerful capabilities provided by SmartGen and its
GUI can simplify the process of including DDR macros in designs and minimize design errors.
Additional considerations should be taken into account by the designer in design floorplanning
and placement of I/O flip-flops to minimize datapath skew and to help improve system timing
margins. Other system-related issues to consider include PLL and clock partitioning.
Part Number and Revision Date
This document contains content extracted from the Device Architecture section of the datasheet,
combined with content previously published as an application note describing features and
functions of the device. To improve usability for customers, the device architecture information has
now been combined with usage information, to reduce duplication and possible inconsistencies in
published information. No technical changes were made to the datasheet content unless explicitly
listed. Changes to the application note content were made only to be consistent with existing
datasheet information.
Part Number 51700094-010-1
Revised March 2008
List of Changes
The following table lists critical changes that were made in the current version of the chapter.
Previous Version
Changes in the Current Version (v1.1)
Page
v1.0
(January 2008)
new.