Timer C interrupt issue
I am using BL4S200. I try use TIMER C to trigger digital output on/off according to presetting time. There are 2 period time need to be counted. 1st period is from 20 msec to 40 msec and need to be accurate, I set 46 micro second tick time. 2rd period is from 4 msec to 30 second. the tick time is supposed to be 0.5 msec or even longer. The program is done by assembly language in order to keep fast response. So after 1st period is finished and digital output is triggered on, I change TCDLR and TCDHR from bigger value to reduce interrupt. The timer C is working properly, but sometimes, Timer C interrupt program doesn't trigger on digital output, even interrupt program is executed. So I try the unique tick time for two period, the program run properly and digital output is triggered properly as well.
Anybody know how to change tick time of timer on line safely?
Thank you for your assistance.