| ??? 09/09/07 20:01 Read: times |
#144181 - WHAT??? Responding to: ???'s previous message |
De Spiegelaere Nico said:
I have a question concerning digital outputs.
I use a 74HCT574 D-type flipflop, as a buffer between my controller and some leds. You DO understand, that you must provide a "clock" input to the 'D' register (HCT574) for each change you expect to see at the device's output, right? When I make a running light it works perfectly when i hold the clock signal (from 574) through a wire in my hand. To what is the "clock" input of the 'HCT574 connected under this condition? What, exactly, do you mean by "running light?" When I connected to ground or positive the runnng light stops. That makes sense, doesn't it? At a DC level, the "clock" input is static, and it must change in order to propagate new data. The data specifications of the 574 say the clock should be an positive raising edge.
Does any of you guys know how to simulate this raising edge or what I should do to make it work. In order to make this sort of approach work, you must apply a positive edge to the "clock" input of the '574 each time you wish to write data to it. That requires that you derive this "clock" signal from some source specific to that function. (The reason for the buffer, is that in a next stadium, I will be adding a shift register to it , so with only a few signals i will be able to control several outputs and inputs.)
This makes sense, but I'm not persuaded that you understand all the required principles. Please answer the following questions. Which 805x variant are you using? Please be very specific, in that you include the package type, and please refer to signal names, and not just pin numbers when addressing the following questions. To which pins of you 805x are the inputs of the '574 attached? How do you create the "clock" input to the '574? RE |
| Topic | Author | Date |
| Digital outputs - running light | 01/01/70 00:00 | |
| don't you have a spare output? | 01/01/70 00:00 | |
| He needs more direction than that! | 01/01/70 00:00 | |
| use HCT573, clock tied to VCC | 01/01/70 00:00 | |
| WHAT??? | 01/01/70 00:00 | |
| 50/60Hz pickup?? | 01/01/70 00:00 | |
The first answer was enough ,thanks | 01/01/70 00:00 |