Basic RTOS is a non-preemptive real time operating system for MSP430 microcontrollers with the following features:

• Non-preemptive
• Round robin as task scheduling
• Tasks with time slice support
• Interrupts are not handled by BRTOS at this moment (user must disable interrupts when running an interrupt routine)

Documentation here (chm).

Seven posts describing the RTOS (In Portuguese): I, II, III, IV, V, VI and VII.