JTAG blocking/unblocking on MSP430F5638

Boris Bychkov said:

To block JTAG via JTAG:

1. set the SYSBSLPE in the SYSBSLC register to 0,
2. set any value other than 0 or 0xFFFFFFFF at addresses 0x17FC to 0x17FF,
3. initiate a Brownout Reset.

To unblock JTAG via BSL (there are no other unblocking ways):

1. set the SYSBSLPE in the SYSBSLC register to 0,
2. set 0 or 0xFFFFFFFF at addresses 0x17FC to 0x17FF,
3. initiate a Brownout Reset.

Yes. Soft JTAG fuse is located inside BSL area (017FCh). Blowing can be done by writing four 055h bytes, and unblow can be done by writing four 000h bytes. For returning fuse values to initial state (0FFh) BSL must be reflashed.

http://forum.43oh.com/topic/2972-sbw-msp430f550x-based-programmer/?p=44019

Boris Bychkov said:

Thank you very much!
According to those posts you created a hand made programmer to program MSP430. And all examples in that topic are for your programmer.
But what hardware and software I need to block/unblock JTAG? Is it necessary for me to assemble and use your programmer? In case I can't do JTAG blocking without your programmer: where I can find any examples suitable for MSP430F5638?

Boris Bychkov said:

1) Explain me please which memory access commands I should use to write values (055h) to BSL memory.
 

Sorry...

1) Explain me please which memory access commands I should use to write values (055h) to BSL memory by application code.

Thank you.

zrno soli said:

Than flash byte / word write can update 017FCh fuse values. Flash write code examples can be found in 5xx / 6xx family datasheet.

Boris Bychkov said:

One more question.
Why I can't copy the BSL segment to INFO segments, then erase BSL segment, then restore BSL data from INFO memory but add my JTAG lock key value (00h, 55h, ffh or another)? Is that proccess possible? It is without festored BSL by special hardware.

Yes, this is possible, and it can be done by your application without special hardware. BSL size is 4 KByte, and Info size is 512 bytes. It will be enough to restore just BSL3 segment (01600h-017FFh, 512 bytes) where JTAG fuse values are stored.

I think application code writing necessary value to BSL flash should consist of the following parts.

1. erase info flash segments (A,B,C,D)
2. write data from BSL3 to info flash
3. erase BSL3 segment
4. write data from info flash to BSL3 (except the last four bytes)
5. write necessary values (JTAG lock key) to the last four bytes in BSL3

The code is here.

1) But what will happen in case a power off occurs during the part 4? Will MSP430 be operability after reset? If the device is all right I think it's possible to write up saved BSL3 data from info flash.

2) Can we use RAM instead of info flash in this algorithm?

//------------------------------------------------------------------------------
// Fill JTAG lock key in BSL flash area with given bytes
// |_ value: a value which JTAG lock key will be fill with
//------------------------------------------------------------------------------
void write_JTAGkey(char value)
{
  unsigned int i;
  char * Flash_ptr;                         // Flash pointer
  char * FlashBSL_ptr;                      // BSL flash pointer
  
  _DINT();                                  // Disable interrupts
  FCTL3 = FWKEY;                            // Clear LOCK bit
  
  // Erase info flash segments A,B,C,D
  FCTL1 = FWKEY|ERASE;                      // Set ERASE bit
  Flash_ptr = (char *) 0x1800;              // Seg D
  *Flash_ptr = 0;                           // Dummy write to erase flash seg
  Flash_ptr = (char *) 0x1880;              // Seg C
  *Flash_ptr = 0;                           // Dummy write to erase flash seg
  Flash_ptr = (char *) 0x1900;              // Seg B
  *Flash_ptr = 0;                           // Dummy write to erase flash seg
  Flash_ptr = (char *) 0x1980;              // Seg A
  *Flash_ptr = 0;                           // Dummy write to erase flash seg
  FCTL1 = FWKEY;                            // Clear ERASE bit
  
  SYSBSLC &= ~SYSBSLPE;                     // Clear SYSBSLPE bit
    
  // Write data from BSL3 to A,B,C,D
  FCTL1 = FWKEY|WRT;                        // Set WRT bit
  Flash_ptr = (char *) 0x1800;              // Seg D
  FlashBSL_ptr = (char *) 0x1600;           // BSL3 seg
  for (i = 0; i < 512; i++)
  {
    *Flash_ptr++ = *FlashBSL_ptr++;         // Copy BSL3 to info flash
  }
  FCTL1 = FWKEY;                            // Clear WRT bit
  
  // Erase BSL3 seg
  FCTL1 = FWKEY|ERASE;                      // Set ERASE bit
  FlashBSL_ptr = (char *) 0x1600;           // BSL3 seg
  *FlashBSL_ptr = 0;                        // Dummy write to erase flash seg
  FCTL1 = FWKEY;                            // Clear ERASE bit
  
  // Write data from A,B,C,D to BSL3
  FCTL1 = FWKEY|WRT;                        // Set WRT bit
  Flash_ptr = (char *) 0x1800;              // Seg D
  FlashBSL_ptr = (char *) 0x1600;           // BSL3 seg
  for (i = 0; i < 508; i++)                 // 512-4=508 byte
  {
    *FlashBSL_ptr++ = *Flash_ptr++;         // Copy info flash to BSL3
  }
  FCTL1 = FWKEY;                            // Clear WRT bit
  
  // Write JTAG lock key to BSL3
  FCTL1 = FWKEY|WRT;                        // Set WRT bit
  FlashBSL_ptr = (char *) 0x17FC;           // JTAG lock key address
  for (i = 0; i < 4; i++)                   // 4 byte
  {
    *FlashBSL_ptr++ = value;                // Fill key with value
  }
  FCTL1 = FWKEY;                            // Clear WRT bit
  
  SYSBSLC |= SYSBSLPE;                      // Set SYSBSLPE bit
  
  FCTL3 = FWKEY|LOCK;                       // Set LOCK bit
  _EINT();                                  // Enable interrupts
}

Boris Bychkov said:

I think application code writing necessary value to BSL flash should consist of the following parts.

1. erase info flash segments (A,B,C,D)
2. write data from BSL3 to info flash
3. erase BSL3 segment
4. write data from info flash to BSL3 (except the last four bytes)
5. write necessary values (JTAG lock key) to the last four bytes in BSL3

The code is here.

1) But what will happen in case a power off occurs during the part 4? Will MSP430 be operability after reset? If the device is all right I think it's possible to write up saved BSL3 data from info flash.

2) Can we use RAM instead of info flash in this algorithm?

Info A segment must be unlocked for flash operations. BSL will not be updated, so you can store last BSL segment to Info only once (together with main memory flashing), forever. Later, it can be recovered from Info anytime. Copy flashing function (erase / block write) to RAM and execute it from there to minimize power-off impact.

zrno soli said:

Info A segment must be unlocked for flash operations.