TMS570LS3137-EP: How to disable unused registers

Hello Ryan,

There are 3 ways of disabling a module:

1. through PMM: you can power down a power domain (PD2, PD3, PD4, PD5) through PMM registers

2. through PCR: to disable the peripheral through PSPPwrDwnSet[x] register. Each peripheral select (PS) addresses a 1KB region. This region is then divided into four quadrants [3 - 0], with each quadrant being 256 bytes. These quadrants are then assigned to individual peripheral module control/status registers. Some peripheral register frames fit within a quadrant, while some other peripherals take two quadrants. Please refer to PCR section in TRM.

https://e2e.ti.com/support/microcontrollers/hercules/f/312/p/785547/2905699?tisearch=e2e-sitesearch&keymatch=PSPWRDWN#2905699

3. through the module registers if available. for example DCAN module can be locally powered down by setting PDR bit in DCAN control register. Please refer to "24.12.1 Entering Local Power Down Mode" in DCAN chapter

All table, section and page references are from spnu449c.pdf unless otherwise noted.

Hey QJ,

I am back on this again and was able to get the PMM items turned off. Thank you for that. Now, I am working on the PCR power down. My first question is:

In Table 2-3 (pages 104-108): What does "unimplemented" mean in "RESPONSE FOR ACCESS TO UNIMPLEMENTED LOCATIONS IN FRAME"
Does "unimplemented" mean powered down via PMM or PCR, or does it mean their init function was never called, or both?

I did look at the link you provided regarding power down Peripherals using the PCR and I am unclear on how to set the Protection registers. Is that required if I am going to power them off?

Finally, I assume if I can power down both the Peripheral Memory and Registers I should do so? (for example MIBSPI5, pages 105 and 107)

Regards,
Ryan

Hi Ryan,

1. Unimplemented ..: The memory location is not actually there. For example, the frame size of NHET1 RAM (0xFF46_0000~0xFF47_FFFF) is 128KB, but the actual size in this device is only 16KB (0xFF46_0000 ~ 0xFF46_0400). The address above the highest real memory (0xFF46_0400) is not implemented.

2. The PCR PPROTSETx and PMPROTSETx registers protect the peripheral registers and memories against illegal writes by the CPU. The CPU can read from the peripheral registers and memories in both user and privileged modes. There is no access protection for real operation. 

The PCR module PMPROTSETx registers contain one bit per peripheral memory frame (PCS[x] in table 2-3). 

The PCR module PPROTSETx registers contain one bit per peripheral select quadrant. These bits define the access permissions to the peripheral register frames (PS[x] in Table 2-3). 

If you are going to power off a module, it doesn't matter to set the protect registers or not.

3. PCSPWRDWNSET[x]: only one bit for one peripheral memory. MibSPI5 RAM is  #5 (PCS[5] in table 2-3). Setting bit 5 of PCSPWRDWNSET[0] will power down this module memory.

    PSPWRDWNSET[x] is to power down the peripheral and was mentioned before. 

Hi QJ,

1. Unimplemented: That makes sense. I was looking at the Peripheral Control Register section, where the Frame Size and Actual Size match, I think that is what confused me. 

2. Protection: In that case, I am not going to set this if I am power it down. 

3. PCSPWRDWNSET[x]: I have gone through and powered down the peripheral registers and associated memory if applicable.

Thank you for your feedback.

New: 

After powering off the items I wanted (like MibSPI5) I noticed that when I ran with the debugger, the MibSpip5 registers were not all zeros. Maybe they dont need to be, but i assumed they would be if the memory and registers were powered off. Here are a few of the ones that are set:

IntFlg: 0x0100_0000 - BUF Init Active (buffer is being initialized)

DIn (Pin Control 2): 0x0F0F_0F0F - basically initializing pin direction and enabling

PSel (Pin Control 8): 0x0F0F_0F0F 

RxBuf: 0x8000_0000 - no data received

Emu: 0x8000_0000 - reserved

DefCs: 0x0000_000F - no transfer active

Overall it seems like these are default values. Is it ok that the registers contain values even though they powered down? (Are these values correct/expected?) 

Best,
Ryan