User`s guide

Continuous/Discrete Conversions of LTI Models
3-25
The step responses of the continuous and discretized models are compared in
the figure below. This plot was produced by the command
step(h,'--',hd,'-')
Note: The Tustin and matched pole/zero methods are accurate only for
delays that are inte ger multiples of the sampling period. It is therefore
preferable to use the
zoh and foh discretization methods for models with
delays.
Delays and Continuous/Discrete Model Conversions
When you apply c2d and d2c to state-space models, all or part of the I/O delay
matrix of the resulting model is absorbed into the input and output delay