From the microchip app note http://ww1.microchip.com/downloads/e...tes/01465A.pdf

The Digitally Addressable Lighting Interface (DALI) has
emerged as a standard in Europe to address growing
power issues, mostly for commercial and industrial
purposes. DALI is part of the IEC 60929 specification,
and relates specifically to digitally controlled dimmable
fluorescent ballasts. DALI type ballasts can run at lower
power levels than standard magnetic ballasts.
Commercial development of DALI started around 1998.
DALI consists of a two-wire serial bus and requires a
special DALI power supply. The Master sends 16-bit
Manchester encoded data packets, and the ballasts
can respond with an 8-bit Manchester encoded data
packet. Multi-Masters are allowed, and two Masters
can share the same ballast. There are 64 channels, or
individual addresses, available for the ballasts to be
connected to one interface line. Each DALI bus can
have 16 groups at the maximum, and there are 16
scenes available. There is no error checking in the
DALI protocol. This application note describes the
basic communication between the control device and
the control gear, which includes explanation of
electrical specifications, timing, packet formats and
Manchester encoding/decoding.