  Most of the devices in the SLAC control system are accessed via interface
modules in ~450 CAMAC crates. Low-cost controllers in these crates communicate
via a SLAC-proprietary bit-serial protocol with 77 satellite control computers
("micros") within the accelerator complex. A proposed upgrade replaces the
existing Multibus-I implementation of the micro hardware with
commercial-off-the-shelf ("COTS") personal computers. For increased reliability
and ease of maintenance, these micros will move from their current electrically
noisy and environmentally challenging sites to the control center's computer
room, with only a stand-alone portion of each micro's CAMAC interface remaining
in the micro's original location. This paper describes the hardware/software
architecture of that intelligent front-end CAMAC controller and the
accompanying fiber optic link board that connects it to the PC-based micro's
PCI bus. Emphasis is placed on the hardware/software techniques employed to
minimize real-time latency for pulse-to-pulse operations that control
accelerator timing, acquire data for fast feedback loops, and change device
settings to close those loops. The controller provides the sole interface
between the COTS computing/networking environment and the existing CAMAC plant.
It also supports higher bandwidth commercial byte-serial crate controllers and
legacy BITBUS hardware.
