When TACTL is modified with a MOV instruction, the contents of TAR may be cleared, even when TACLR is not set.
Workaround
Use BIS or BIC instructions to modify TACTL.
Note:
A DMA transfer must not occur while these BIS and BIC instructions execute. This can be prevented by disabling the DMA prior to these instructions, or by using the DMAONFETCH bit to align DMA transfers to instruction fetch boundaries.