We report on the charge transfer dynamics between a silicon quantum dot and an individual phosphorous donor extracted from the current through the quantum dot as a probe for the donor ionization state. We employ a silicon n-metal-oxide-semiconductor field-effect transistor (MOSFET) with two side gates at a single metallization level to control both the device conductance and the donor charge. The elastic nature of the process is demonstrated by temperature and magnetic field independent tunneling times. The Fano factor approaches 1/2 revealing that the process is sub-poissonian.