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AR# 8292

*Obsolete* JTAG - Using the TDO pin as a user output on XC4000 based devices (HDL example)

Description

Keywords: VHDL, TDO, user, output

Urgency: Standard

General Description:
How do you use the TDO pin as user output?

解决方案

1

To use TDO as user output, you must instantiate the TDO pin. Do not just lock an output to the TDO pin; this will cause an error in NGDBuild.

2

-- Using the TDO pin as user output
-- Example code of how to instantiate TDO
-- To be used as a guide only

library IEEE;
use IEEE.std_logic_1164.all;

entity test_tdo is
port (D_IN, D_IN2, CLK: in std_logic;
Q_OUT: out std_logic);
end test_tdo;

architecture xilinx of test_tdo is

component obuf
port(i: in std_logic; o: out std_logic);
end component;

component TDO
port ( O : in std_logic );
end component;

signal TDO_INT, TDO_P : STD_LOGIC;

begin

TDO_Inst: TDO port map (O => TDO_P);
OBUF_Inst: obuf port map(i=>TDO_INT, o=>TDO_P);

-- User logic here
process (CLK)
begin
if (CLK'event and CLK='1') then
Q_OUT <= D_IN;
TDO_INT <= D_IN and D_IN2;
end if;
end process;

end xilinx;
AR# 8292
创建日期 08/31/2007
Last Updated 09/26/2005
状态 Archive
Type ??????