Effects of Response Time / 响应时间的影响
Now that we know about response time, here's what it really means to the application. The PLC can only see an input turn ON/OFF when it's looking. In other words, it only looks at its inputs during the check input status part of the scan.
现在我们知道了响应时间，下面就说说它对应用程序的真正含义。PLC只有在查找输入状态时才能看到输入点是开还是关。换句话说，它只在一个扫描阶段的输入状态检查部分才查看其输入。(一个扫描阶段包含：输入状态检查部分—程序执行部分—输出状态更新部分)
In thediagram, Input 1 is not seen until scan 2. This is because when input 1 turned ON, scan 1 had already finished looking at the inputs.
Input 2 is not seen until scan 3. This is also because when the input turned ON scan 2 had already finished looking at the inputs.
Input 3 is never seen. This is because when scan 3 was looking at the inputs, signal 3 was not ON yet. It turns OFF before scan 4 looks at the inputs. Therefore signal 3 is never seen by the plc.
在上面时序图中，直到第2扫描阶段(SCAN2)才能看到输入1的打开状态。这是因为当输入1打开时，第1扫描阶段(SCAN1)已经完成了对输入1的状态的查看。
直到第3扫描阶段(SCAN3)才能看到输入2的打开状态。这也是因为当输入2打开时，第2扫描阶段(SCAN2)已经完成了对输入2的状态的查看。
永远看不到输入3的打开状态。这是因为当第3扫描阶段(SCAN3)查看输入3的状态时，输入3还没有打开，但在第4扫描阶段(SCAN4)查看输入状态时它又已经关闭。因此，输入3的打开状态永远不会被PLC看到。
To avoid this we say that the input should be on for at least 1 input delay time + one scan time.
为了避免这种情况，我们说输入打开时间应该至少有一个输入延迟时间加上一个扫描周期时间。
But what if it was not possible for the input to be ON this long? Then the plc doesn't see the input turn ON. Therefore it becomes a paper weight! Not true... of course there must be a way to get around this. Actually there are 2 ways.
但是如果输入不可能有这么长时间呢？然后，PLC就看不到输入打开的状态。那么我们就不用管这种情况了吗？不，不，那是不行的……当然，肯定有办法解决这个问题。实际上有两种方法解决这个问题。
Pulse stretch function: This function…… extends the length of the input signal until the plc looks at the inputs during the next scan.( i.e. it stretches the duration of the pulse.)
脉冲扩展功能:该功能扩展输入信号的长度，直到PLC在下一次扫描周期内查看输入信号。(即，它延长了脉冲的持续时间。)
Interrupt function: This function interrupts the scan to process a special routine that you have written. i.e. As soon as the input turns ON, regardless of where the scan currently is, the PLC immediately stops what its doing and executes an interrupt routine. (A routine can be thought of as a mini program outside of the main program.) After its done executing the interrupt routine, it goes back to the point it left off at and continues on with the normal scan process.
中断功能：此功能可以中断扫描，以处理您编写的特殊例程。例如，只要输入打开，无论当前扫描周期在哪里，PLC都会立即停止它正在做的事情，并执行中断例程。(例程可以看作是主程序之外的一个小程序)。在它执行完中断例程之后，它回到它停止的地方，继续它正常的扫描过程。
Now let's consider the longest time for an output to actually turn ON. Let's assume that when a switch turns ON we need to turn ON a load connected to the PLC output.
The diagram below shows the longest delay (worst case because the input is not seen until scan 2) for the output to turn ON after the input has turned ON.
The maximum delay is thus 2 scan cycles - 1 input delay time.
现在让我们考虑一个输出点实际打开的最长时间。让我们假设，当一个输入点打开时，我们需要打开一个连接到PLC输出点上的负载。
下面时序图显示了输入点打开后输出点打开的最长延迟时间(最坏的情况是直到第2扫描阶段SCAN2才看到输入点打开状态)。
因此最大的延迟时间是2个扫描周期时间减去1个输入延迟时间。
It's not so difficult, now is it ? / 这并不难，不是吗？