receiver characterization in CCS

   I read the white paper of Synopsys's CCS (composite current source model) model, but I can't understand the receiver model of CCS.
   In the paper, it is said the receiver consists of C1 and C2. C1 is used before the delay trip point has been reached and C2 is used after the delay trip point has been reached.

   so there is no miller cap in receiver?
   C1 and C2 are both ground cap connected to input node?
   In the simulation, the capacitance of receiver is switched between C1 and C2, it will produce noncontinuous waveform due to the sudden change.
   then I feel confused.

   Please help me!