  We report results from simultaneous ASCA and RXTE observations of Cyg X-1
when the source made a rare transition from the hard (= low) state to the soft
(= high) state in 1996. These observations together cover a broad energy range
~0.7--50 keV with a moderate energy resolution at the iron K-band, thus make it
possible to disentangle various spectral components. The low-energy spectrum is
dominated by an ultra-soft component, which is likely to be the emission from
the hottest inner portion of the accretion disk around the black hole. At high
energies, the X-ray spectrum can be described by a Comptonized spectrum with a
reflection component. The Compton corona, which upscatters soft ``seed
photons'' to produce the hard X-ray emission, is found to have a y-parameter
~0.28. The hard X-ray emission illuminates the accretion disk and the
re-emitted photons produce the observed ``reflection bump''. We show that the
reflecting medium subtends only a small solid angle ($\sim 0.15\times 2\pi$),
but has a large ionization parameter such that iron is ionized up to
\ion{Fe}{24}-\ion{Fe}{26}. The presence of a broad iron line at $6.58\pm0.04$
keV is also consistent with a highly ionized disk, if we take into account the
gravitational and Doppler shift of the line energy. These results imply a
geometry with a central corona surrounding the black hole and the reflection
occurring in the innermost region of the disk where matter is highly ionized.
