AR# 12946


7.0 SYNPLIFY - Problem involving instantiated BUFGCEs


General Description:

Synplify 7.0 does not recognize an instantiated BUFGCE as a clock buffer; therefore, Synplify 7.0 will infer an IBUF instead of an IBUFG for the PAD.


VHDL Example

BUFGCE instantiation using Synplify:

library ieee;

use ieee.std_logic_1164.all;

use ieee.std_logic_signed.all;

entity bufgce_instantiate is

port ( clk_pad : in std_logic;

ce : in std_logic;

a : in std_logic_vector(15 downto 0);

b : in std_logic_vector(15 downto 0);

p : out std_logic_vector(31 downto 0) );

attribute xc_padtype: string;

attribute xc_padtype of clk_pad: signal is "IBUFG";

-- this attribute forces external clock pad signal to be of type IBUFG instead

-- of IBUF inferred by default by Synplify

end entity bufgce_instantiate;

architecture structural of bufgce_instanciate is

signal clk : std_logic;

component BUFGCE

port ( O : out std_logic;

CE : in std_logic;

I : in std_logic );

end component;


-- BUFGCE instanciation


port map ( O => clk,

CE => ce,

I => clk_pad);

-- other code

process (clk)


if rising_edge(clk) then

p <= a * b;

end if;

end process;

end architecture structural;

Verilog Example

BUFGCE instantiation using Synplify:

module bufgce_instantiate (clk_pad, ce, a, b, p);

input clk_pad /* synthesis xc_padtype = "IBUFG" */;

input ce;

input a;

input b;

output p;

wire clk;

BUFGCE U1 (.O(clk), .CE(ce), .I(clk_pad));

always @(posedge clk) p <= a * b;

AR# 12946
Date 01/20/2011
Status Archive
Type General Article
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