The BaBar collaboration has chosen the Controller Area Network (CAN) [1] bu
s for its controls and monitoring field bus. In addition. the Motorola MC68
HC70SX32 [2] microcontroller, which has a CAN interface, was chosen for the
standard intelligent device for monitoring boards. This paper describes th
e CAN system used by BaBar and the embedded software that supports it. The
General Monitoring Board (GMB) is presented as a specific example. The GMB
is a CAN module that digitizes 32 differential analog signals and has eight
bits of bi-directional I/O.