[C5535] Confirm the behavior difference between Hardware reset and Software reset

Hi Kaka-san,

Below are my response:

Q1 Would you please teach me the reset behavior difference between hardware and software?

Hardware Reset - Hardware reset is responsible for initializing all key states of the device. When a hardware reset is asserted, all the registers are set to their default values. The hardware reset occurs whenever the RESET pin is asserted or when the internal power-on-reset (POR) circuit de-asserts an internal signal called POWERGOOD. Once the hardware reset is applied, the DSP starts the boot sequence. More details on reset are in C5535 datasheet section 5.7.3 which you might be already aware off.

Software reset - there are two types of software reset: the CPU's software reset instruction and the software control of the peripheral reset signals.

Software instruction reset only affects IFR0, IFR1, ST0_55, ST1_55, ST2_55, all 16 bits of T2 register, and SATA bit in ST3. All other registers are unaffected. This will generate software interrupt.

To note: A hardware reset loads the interrupt vector pointer called IVPD with FFFFh and, thus, forces the CPU to fetch the reset vector from program address FF FF00h. During a software reset, IVPD remains unchanged; the CPU fetches the reset vector using the current IVPD value.

With respect to software control of the peripheral reset, this reset can be applied either through PRCR (peripheral reset control register) or in some peripherals it can be through specific software reset bit.

Q2 :Will the C5535 reboot the device after software Reset?

I think this actually depends on what is implemented as part of software reset interrupt routine (the next jump address ). The software reset instruction will generate software interrupt but during software reset, IVPD remains unchanged; the CPU fetches the reset vector using the current IVPD value , which customer can change it any time.

Hope this information helps . Pl let us know if you have additional questions on the above.

Regards

 Vasanth