  We studied generation and dynamics of solitonic pulses, platicons, at normal
group velocity dispersion due to the pump amplitude modulation. We proposed,
that if the required frequency of amplitude modulation is too large for
available modulators, it is possible to use subharmonic phase modulation for
platicon generation. It was also demonstrated that it is possible to control
the repetition rate of platicons by tuning modulation frequency. Tuning range
for platicons was found to be much wider than for bright solitons. We also
studied the influence of the high-order dispersion on platicon properties. It
was shown that both third-order dispersion and pump modulation govern platicon
dynamics making it quite different from dynamics of dissipative Kerr solitons.
Third-order dispersion was also shown to affect significantly the optimal
conditions for the platicon generation and repetition rate tuning range.
