interfacing the basic stamp to the 74ls373 latch

Vertex78

I am trying to figure out how to use this chip correctly, I though I had it figure out but I cannot get this circuit to work.

I am using the basic stamp board of education to breadboard this chip and interface to the stamp. I have the power and ground connections made, and then d0 - d7 doing to stamp pin0 - pin7. Then I have the latch pin 1 (OE) connected to stamp pin 9 and latch pin 11 (LE) connected to stamp pin 8.·

So I am trying to load data onto the data lines then latch the data in, then change the data on the data lines and then using a logic probe verify that the data stays the same on the latch output, since the changed data was never latched into the chip. But it does not appear to be latching my data, it just shows whatever is at the inputs on the outputs.

Here is my code

HIGH 9··· 'disable outputs
HIGH 8·· 'LE high

'load data onto latch inputs
LOW·0
HIGH·1
HIGH·2
HIGH·3
HIGH·4
HIGH·5
HIGH·6
HIGH·7

LOW 8··· 'latch data
PAUSE 500·· 'delay to allow latch to settle
HIGH 8·· 'finished latching data

LOW 9· 'enable outputs

HIGH 0 ' since pin0 was set low then latched into chip this value should not show up on latch output, but it does.
·

Phil Pilgrim (PhiPi)

You've got the sense of the LE line backwards. When it's high, the latch is transparent. When it's low, the data is latched. Just delete the PAUSE and the last HIGH 8, and your program should work.

-Phil

Vertex78

I took out the pause and the high 8 but it still does the same thing. I tried replacing the chip to make sure it was not deffective and double checked the wiring. Still does the same thing. Perhaps I have two bad chips?

Phil Pilgrim (PhiPi)

Can you post a photo of your breadboard and your current complete program listing? (Please post your program between [noparse][[/noparse]code] and &#091/code] tags this time.)

-Phil

Vertex78

I figured it out, I was leaving out the '{PBASIC 2.5} and I was not terminating the programming correctly. Thanks for the help.

KatyBri

Vertex78,

Would you pleasepost your final code that worked? Thanks.