CTRLSTAT = 0xffffffff

Hi and welcome to the community.

Which tool are you using for reading the data ?

(Maybe OpenOCD - or your own ?)

-Can you provide some extra information about the microcontroller vendor and model number ?

(it might be helpful in finding out the cause and thus the solution).

Thank you for responding, and by the way i am using stm32f407vg as host and stm32f407vg as target .i am trying to implement debug functionality so that i could access/control target from host. i put a step forward with Mark's Space: Programming internal SRAM over SWD blog.

i am taken 2 gpio pins configuration as follow

/* preparing GPIO pin to SWDIO */

GPIO_PIN_DATA_t st_gSWDIOPin =

{

  GPIO_PORTE,

  PORT_PIN3,

  GPIO_MODE_OUT,

  GPIO_OTYPE_PP,

  GPIO_SPEED_50MHz,

  GPIO_PUPD_NOPULL

};

/* Preparing GPIO pin to clock  */

GPIO_PIN_DATA_t st_gSWDCLKPin =

{

  GPIO_PORTE,

  PORT_PIN2,

  GPIO_MODE_OUT,

  GPIO_OTYPE_PP,

  GPIO_SPEED_50MHz,

  GPIO_PUPD_NOPULL

};

as a first step i send signals from host to target and able to read IDCODE,and even i am able to write CTRLSTAT register with value 0x50000000 but when i am trying to read CTRLSTAT .I got ACK success but while i am reading i got 0xffffffff,

hoping thins information might helpful to you for my problem

Thanks & Regards.

For STMicroelectronics's own documentation on the subject, please see RM0090, section 38.3.1.

First of all, we'll need to make sure your connection is OK.

When I connect a JTAG-Lock-pick Tiny 2 to my targets, I use the standard JTAG pull-up and pull-down resistors:

• TCLK/SWDCLK: 10K pull-down
• TMS/SWDIO: 10K pull-up
• TDO/SWO: 10K pull-up

... Next, do you switch from output to input, when you're reading the CTRL/STAT register ?

... Also... The address; are you encoding it correctly, so (only) bits 3 and 4 in the first byte you send are modified ?

... If you have a logic-analyzer, it might be a good idea to connect it, in order to monitor the values sent and received on the pins.

... If you have a logic-analyzer, try monitoring the data that OpenOCD transfers to the target when it starts up, then compare to your own data.

I know this sounds ridiculous, but it is a very good idea to write some low-level debug code, which shows you exactly what is going on.

It will probably be a good idea to make a temporary modification to your transmit routine, the one routine, that sends a single bit:

It should output either a 0 or a 1, depending on the data it sends.

Then after each stream of bits, you send output a space.

Finally, at the end of each transfer, you output a newline character.

Transmit all the data from above to your debug-terminal via a UART interface, if you have a terminal connected to the board.

Example of making the code fast (do not use printf in your bit-transmitter code):

1: Create a static buffer and a static pointer variable outside your transmission function:

static char sDebugBuffer[128];

static char *pDebugBufffer = sDebugBuffer;

2: Before starting each transmission, do the following:

pDebugBuffer = sDebugBuffer;

3: Each time you transmit a bit, do the following:

*pDebugBuffer++ = '0' + bitValue;

4: Each time you're done transmitting a sequence of bits (for instance 8 bits for a byte, or 3 bits for the response code, or 33 bits for the WDATA, do the following:

*pDebugBuffer++ = 0x20;

5: Each time a transfer ends, do the following:

*pDebugBuffer++ = 0x0a;

*pDebugBuffer = 0x00;

pDebugBuffer = sDebugBuffer;

/* and write the contents of the debug-buffer to your UART; maybe you're using UART_send, maybe write, maybe printf, let's assume printf in this case: */

printf("%s", sDebugBuffer);

This enables you to verify that your transmission is correct length, and it will also enable you to see exactly what bit-values are sent, so you can verify they're what you expect them to be.

For the response, you can of course also implement a similar mechanism.

from Implementation of Serial Wire JTAG flash programming in ARM Cortex M3 Processors | Theesan's log  "Table 2.2.1 DP Register information" he given in 3:2 order i am taken in 2:3 order so

a[2:3] = 1 | 0

Parity = 1

Stop = 0

Perk = 1

in hex 0x95

To Read  CTRLSTAT 

startbit  = 1

APnDP = 0

R/W     = 1

from Implementation of Serial Wire JTAG flash programming in ARM Cortex M3 Processors | Theesan's log Table 2.2.1 DP Register information he given in 3:2 order i am taken in 2:3 order so

a[2:3] = 1 | 0

Parity = 0

Stop = 0

Perk = 1

in hex B1

HardwareDebugConnections - ** Code Red Support Site **

from the above url i connected host GPIO to SWCLK pin of target with 10k pull down, and host GPIO to SWDIO pin of target with 10K pullup. is there any wrong with hardware connection??