Revisions Affected

0, A, B

Details

When the CLKSRCCTL1 register is written more than once without delay between writes, the system can hang and can only be recovered by an external XRSn reset or Watchdog reset. The occurrence of this condition depends on the clock ratio between SYSCLK and the clock selected by OSCCLKSRCSEL, and may not occur every time.

If this issue is encountered while using the debugger, then after hitting pause, the program counter will be at the Boot ROM reset vector.

Implementing the workaround will avoid this condition for any SYSCLK to OSCCLK ratio.

Workaround

Add a software delay of 300 SYSCLK cycles using an NOP instruction after every write to the CLKSRCCTL1 register.

Example:

ClkCfgRegs.CLKSRCCTL1.bit.INTOSC2OFF=0;         // Turn on INTOSC2
asm("  RPT #250 || NOP");                       // Delay of 250 SYSCLK Cycles
asm("  RPT #50 || NOP");                        // Delay of 50 SYSCLK Cycles
ClkCfgRegs.CLKSRCCTL1.bit.OSCCLKSRCSEL = 0;     // Clk Src = INTOSC2
asm("  RPT #250 || NOP");                       // Delay of 250 SYSCLK Cycles
asm("  RPT #50 || NOP");                        // Delay of 50 SYSCLK Cycles

C2000Ware_3_00_00_00 and later revisions will have this workaround implemented.