最近在看MIPI D-PHY spec v1-2发现有一些平常可能不太会关注的点，但是有部分在实际调试mipi的时候确十分有帮助的点，在此列出：

timing参数中hs-zero和hs-trail的作用

关于发送数据前的hs_zero和hs_trail的作用：To aid receiver synchronization, data bursts shall be extended on the transmitter side with a leader and trailer sequence and shall be eliminated on the receiver side.看来是有助于RX同步数据，RX接收解析数据的时候会丢弃这部分数据。

timing参数定义

timing参数有部分是绝对时间，有部分和UI有关系，

具体原因：

1. The explicit time values, in general, are derived from the time needed to charge and discharge the interconnect to its specified values given the specified drive voltages and line termination values. 如果时间参数的值是根据到特定电压或者line终端值的充放电时间决定，就只需要具体时间。

2. If these explicit time values are implemented by counting HS clock cycles only, the count value is a function of the data rate and, therefore, must be changed when the data rate is changed。如果时间参数的值根据HS cycle计数得到，则该参数会随data_rate改变而改变，因此单位和UI有关

Forward High-Speed Data Transmission Timing

Data is launched in a quadrature relationship to the clock such that the Clock signal edge may be used directly by the receiver to sample the received data。时钟和相位需要正交。

The transmitter shall ensure that a rising edge of the DDR clock is sent during the first payload bit of a transmission burst such that the first payload bit can be sampled by the receiver on the rising clock edge。第一笔传输需要在时钟的上升沿。这里可以参考上面HS Data Transmission Burst时序图里面capature 1st data bit的位置。笔者之前在调试mipi dsi的时候，就发生过由于第一笔传输没有在时钟的上升沿，导致屏幕不亮的情况。