Megafunctions

altddio_in (DDIO Input) Megafunction

Double Data Rate (DDR) input megafunction. The altddio_in megafunction receives data on both edges of the reference clock. The altddio_in megafunction is available for APEX™ II, Cyclone™, Mercury™, Stratix™, and Stratix™ GX devices only.

This topic contains the following information:


AHDL Function Prototype (port name and order also apply to Verilog HDL):

 
FUNCTION altddio_in (datain[(WIDTH) - (1)..0], inclock, inclocken, aclr, aset)
   WITH (WIDTH, POWER_UP_HIGH, INTENDED_DEVICE_FAMILY)
   RETURNS (dataout_h[(WIDTH) - (1)..0], dataout_l[(WIDTH) - (1)..0]);


VHDL Component Declaration:

 
COMPONENT altddio_in
    GENERIC 
       (WIDTH		: POSITIVE	:= 1;
        POWER_UP_HIGH	: STRING  	:= "OFF");
		
    PORT (data_in 		: IN STD_LOGIC_VECTOR(WIDTH-1 DOWNTO 0);
          inclock 		: IN STD_LOGIC;
          in_clocken 		: IN STD_LOGIC := 1; 
          aclr, aset 		: IN STD_LOGIC := 0;
          dataout_h, dataout_l 	: OUT STD_LOGIC_VECTOR(WIDTH-1 DOWNTO 0);
END COMPONENT;


Port Descriptions:

INPUT PORTS

Port Name Required Description Comments
data_in[] Yes DDR input data port. Input port WIDTH wide. The data_in port should be directly fed from an input pin in the top-level design.
inclock Yes Clock signal to sample the DDR input. The data_in port is sampled on each clock edge of the inclock signal.
inclocken No Clock enable for the data clock.  
aclr No Asynchronous clear input. The aclr port and the aset port cannot be connected at the same time.
aset No Asynchronous set input. The aclr port and the aset port cannot be connected at the same time.

OUTPUT PORTS

Port Name Required Description Comments
dataout_h[] Yes Data sampled from the data_in[] port at the rising edge of the inclock signal.  
dataout_l[] Yes Data sampled from the data_in[] port at the falling edge of the inclock signal.  


Parameter Descriptions:
Parameter Type Required Comments
WIDTH Integer Yes Width of the data_in, dataout_h, and dataout_l ports.
POWER_UP_HIGH String No When both the aset and aclr ports are unused, the POWER_UP_HIGH parameter is available to specify the power-up state of the output ports. Values are "ON", and "OFF". If omitted, the default is "OFF".
INTENDED_DEVICE_FAMILY String No This parameter is used for modeling and behavioral simulation purposes. Create the altddio_in megafunction with the MegaWizard® Plug-in Manager to calculate the value for this parameter.


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