您好，
请教一个关于overall latency 的问题
下图有个ADC的Overalllatency定义=ADClatency+tPDI.
ADC latency 是一个采样到最后输出的时间 ：典型值14个clock，也就是14*4=56ns
tPDI是时钟送入ADC到输出ADC的时间：典型值10.5ns，
我的疑问是：某个时刻250MHz时钟送入ADC，ADC是立刻开始采样模拟信号的吗？如果是的，那过了10.5ns时钟就会输出ADC，而第一个采样点需要56ns才输出，那overall latency应该是56ns，而不是手册上说的56+10.5=66.5ns。是我理解的哪里有问题？多谢！
您好,以LM97937为例,几个latency的定义:
Sample-to-Serial Out (S2SO) Latency—S2SO is the latency from when the signal is sampled at the ADC input until the sample appears in the serial stream at the ADC (TX) output.
Link Delay—Link delay is the delay from when the sampled parallel data is input to the serializer at the transmitter (ADC) until the same data is presented at the input to the elastic buffer.
Link Latency—Link latency is the latency from when the sampled parallel data is input to the serializer at the transmitter (ADC) until the same data is available in parallel form at the receiver.
Sample-to-Parallel Out (S2PO) Latency—S2PO is the latency from when the signal is sampled at the ADC input until the sample is released on the parallel bus at the receiving device (RX).
所以14个clock指的是从ADC采样到ADC输出的latency,而link latency指的是ADC输出数据到Serializer输入直到deserializer 解串出来的数据之间的延迟..
因此overall latency=ADC core latency+link latency=56ns+10.5ns=66.5ns.
