[SOLVED] How to connect I/O of Spartan 2e with PC parallel port?

[picus]

Spartan 2e Help

Hi all,
I have a problem.
I want to connect I/O spartan 2e device Slave(powered to 3.3V and not 5V tollerant CMOS) with PC Parallel Port device Master to 8 bit data transfer.
Can I use 74HC244 buffer ?

Thanks all

 

[Big Boy]

Re: Spartan 2e Help

HC devices does not work well with TTL output. HCT have TTL compatible inputs, but are 5V-rated only.

You better go with 74AHC devices (ex: 74AHC245). Then, the only thing you need is resistors at each output of the parallel port, in series, to the chip input (port -> chip direction). 300ohm is recommended.

You don't need resistors in the chip -> parallel port direction, or on the FPGA side.

You power the chip with 3.3V, the resistors are to limit the current if the parallel port output levels greater than 3.3V. Xilinx download cables use 74AHC series.

 

[kk_10]

Re: Spartan 2e Help

You better go with 74AHC devices (ex: 74AHC245). Then, the only thing you need is resistors at each output of the parallel port, in series, to the chip input (port -> chip direction). 300ohm is recommended.