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Tool/software: Code Composer Studio
Hi
I generated pwm code by HAL but I couldnot understand the meaning of these two lines
hetRAM->Instruction[(pwm << 1U) + 41U].Control = ((hetRAM->Instruction[(pwm << 1U) + 41U].Control) & (~(uint32)(0x00000018U))) | (action << 3U);
hetRAM->Instruction[(pwm << 1U) + 41U].Data = (((pwmPeriod * pwmDuty) / 100U) << 7U) + 128U;
Please explain what is happening and how are the shift operators used.
Why does pwmduty has to be left shifted by 7 and then why 128 is added
Also in control setting, why is action shifted left 3 bits and why 18 is OR with action
Hi Rajat,
These are instructions used in the pwmSetDuty function for example. HALCoGen uses a template High-End-Timer (HET) program and then customizes it based on the user configuration of PWMs and input captures.
Consider the set of instructions for PWM1 as an example. This is a set of 4 instructions:
CNT
PWCNT
DJZ
MOV64
The instruction at (1<<1 + 41) is instruction number 43, which is the MOV64 instruction corresponding to PWM1. Now look at the "control" field of the MOV64 instruction in the TRM.
The control field is first read, then AND'ed with ~(0x18) and then OR'ed with the selected "action". This essentially is a read-modify-write operation that only updates the "Action" in the above control field.
Now consider the data field of the MOV64 instruction:
This data field is made up or a 7-bit high-resolution data field and a 25-bit loop-resolution data field. This HALCoGen example does not use the high-resolution capability, so the "HR Data" field is not used. This is why the updated data value is shifted by 7 and then an offset of 128 is added (2^7 = 128).
Hope this helps.
Regards, Sunil
