eeek

回復  eeek

Thanks. 我見到大部份都係pull high, switch 就接地.
quoy 發表於 2013-6-18 12:56

其實 pull high pull low 只係睇你個 circuit 嘅要求.....啫係 case by case.

quoy

回復 96# eeek

唔似switch bounce 問題, 因為我之前唔用switch , 用飛線篤都係咁.....

我不過我就唔知點解

eeek

回復  eeek

唔似switch bounce 問題, 因為我之前唔用switch , 用飛線篤都係咁.....

我不過我就唔知點解 ...
quoy 發表於 2013-6-18 16:32

我覺得 "飛線篤" 同 switch bounce 一樣. 你有 scope, 可以用 1ms/div check "飛線篤" 同 switch 嘅 waveform.

eeek

回復 102# quoy

A typical switch-bounce waveform:
http://www.labbookpages.co.uk/electronics/debounce.html

"飛線篤" 嘅 waveform 應該相似

quoy

回復 104# eeek

你唔記得我之前張圖. 上果下250us左右, 我諗可能要睇到ns. 下次得閒會再度下.

eeek

回復  eeek

你唔記得我之前張圖. 上果下250us左右, 我諗可能要睇到ns. 下次得閒會再度下. ...
quoy 發表於 2013-6-18 17:13

你呢個 waveform 是有 capacitor 的.
Mechanical switch 唔需要睇到 ns.

FYI,
"Slow clock edge causing issues with D flip flop behavior"
http://electronics.stackexchange ... -flip-flop-behavior

quoy

回復 106# eeek

Thanks.
佢裡面有人提到:
the input transition rate is given as 10 ns/V maximum. This means that you need to make the clock rise or fall by 5 volts in no more than 50 ns in order for the chip to operate correctly. With an RC time constant of 10 ms, you are about 6 orders of magnitude too slow.

如果係真, 我睇我呢個circuit 好難做到咁快

eeek

回復  eeek

Thanks.
佢裡面有人提到:
the input transition rate is given as 10 ns/V maximum. This mea ...
quoy 發表於 2013-6-19 11:25

總結一下, 你提出的兩個方法 (FF 前加 RC, FF前只加 pull-up R) 有以下問題:
1) FF 前加 RC 解決了 switch bounce, 但製造了 slow rising/falling edge, FF 的 CP 受不了;
2) FF 前只加 pull-up R, 有 switch bounce 問題.

唔試吓加 schmit trigger (74HC14 or similar), 我就再無乜 suggestion 了.

quoy

回復 108# eeek

74HC14 我冇....同粒野好似好大.

唔知用一粒AND gate 得唔得...可能又有timing 要求

eeek

回復  eeek

74HC14 我冇....同粒野好似好大.

唔知用一粒AND gate 得唔得...可能又有timing 要求 ...
quoy 發表於 2013-6-19 11:57

ON Semi 有細粒的:
http://www.onsemi.com/pub_link/Collateral/NL17SH17-D.PDF
http://www.onsemi.com/pub_link/Collateral/NL17SH14-D.PDF
http://www.onsemi.com/pub_link/Collateral/NL27WZ14-D.PDF

普通 AND gate 唔得, 除非佢係 schmit-trigger input. Or 74HC132:
"74HC132 Quad 2−Input NAND Gate with Schmitt−Trigger Inputs"
http://www.onsemi.cn/pub_link/Collateral/74HC132.REV1.PDF