  In this paper we present a fully selfconsistent SSC model with particle
acceleration due to shock and stochastic acceleration (Fermi-I and
Fermi-II-Processes respectively) to model the quiescent spectral energy
distribution (SED) observed from PKS 2155. The simultaneous August/September
2008 multiwavelength data of H.E.S.S., Fermi, RXTE, SWIFT and ATOM give new
constraints to the high-energy peak in the SED concerning its curvature. We
find that, in our model, a monoenergetic injection of electrons at $\gamma_0 =
910$ into the model region, which are accelerated by Fermi-I- and
Fermi-II-processes while suffering synchrotron and inverse Compton losses,
finally leads to the observed SED of PKS 2155-30.4 shown in H.E.S.S. and
Fermi-LAT collaborations (2009). In contrast to other SSC models our parameters
arise from the jet's microphysics and the spectrum is evolving selfconsistently
from diffusion and acceleration. The $\gamma_0$-factor can be interpreted as
two counterstreaming plasmas due to the motion of the blob at a bulk factor of
$\Gamma = 58$ and opposed moving upstream electrons at moderate Lorentz factors
with an average of $\gamma_u \approx 8$.
