he CFA and the Open AUC Project make rapid optical system development possible. The following specialized circuits and driver software will be available for optics developers. With these tools new optical systems (e.g. Raman, low angle X-ray scattering) can be developed for AUC. Rotor timing pulse and master clock All data acquisition must be synchronized to the spinning rotor, and a rotor timing pulse with jitter <1 part in 4,000 is critical (Laue et al. 1984). The CFA meets this specification, and a digital rotor timing pulse is provided on the CFA signal bus. The master clock automatically provides 500 kHz pulses below 7,000 rpm and 4 MHz above 7,000 rpm (with hysteresis to avoid switching back until 4,000 rpm). After each rotation, the period of rotation is latched and made accessible on the CFA signal bus, as is whether the low frequency or high frequency clock is being used (Laue et al. 1984).
Synchronizer The synchronizer uses the master clock to modulate either a light source or the detector so that data acquisition starts at a constant fraction of a revolution (the delay) and occurs over some fraction of a revolution (the duration), while compensating for propagation delays. The Open AUC Project synchronizer handles these functions using settings supplied by an external computer on the CFA signal bus (Laue et al. 1984).
Digital data acquisition and data storage A board with a 14-bit 5 MHz A/D with an addressable 16-bit by 4 Mb buffer storage is available for the CFA signal bus. Digitizing may be gated externally (e.g. by synchronizer delay/duration functions). Data are stored sequentially in memory. Additional memory boards may be cascaded to provide up to 15 banks of memory to allow continuous data acquisition over long periods, such as required by the light scattering detectors (Mächtle 1999a). Memory may be accessed from the external computer over the CFA signal bus.