Re: BUFFERS

--- In CAD_CAM_EDM_DRO@y..., "Lloyd Leung" <lloyd@l...> wrote:

> To get the specs for most chips... just go to www.google.com and

type

> the "chip number" and append ".pdf"; i.e. "74HCT244.pdf" will pop up
> links to adobe acrobat documents containing specifications you

desire.

>
> Cheers
>
> PETER,
> HOW DO YOU CONNECT THE 74HCT244 BUFFERS FOR THE PARALLEL PORT?
> THANK YOU,
> AL

After you have the specs note that there are two sections to the
244. Each one has its own enable (negative true). If you look at
the logic table the outputs follow the inputs (non-inverting buffer)
as long as the enable pins are low (ground). Taking the pins high
makes the outputs in that section go into a high impedence
state...basically an open circuit. Be sure to provide VCC (+5V) and
GND (0V) to the correct power pins. The 74HCT541 is essentially the
same thing but the input and output for each gate is physically
opposite each other on the chip, making wiring or PC board layout
easier (for whatever that's worth). Just match up an input for the
signal coming from the parallel port (let's say pin2 is step for your
X channel) and tie the output of that same gate to wherever the pin2
signal is supposed to go (step input for the X channel on the motor
control card). Which buffer gate you use on which signal does not
matter as long as you get them all buffered. To test you could use
LED's with the anode tied to +5, the cathode tied to a 470 ohm
resistor and the other end of the resistor to the output of the gate
(s). The leds will turn off and on with the step and direction
signals. Disconnect the LEDs before using it to drive the real
circuit. Happy soldering!