Posted on February 07, 2005 at 04:04I am currently working on ST72F561 MCU at 16 MHz. I am facing serious problem regarding the Start up behavior of the MCU. When I switch the power supply (Regulated 5V DC) to the MCU, I found that sometimes the I/O ports show indeterminist behavior. Since these pins are connected to external output loads, they come ON momentarily at Power-on.
I have following set-up :
1. I use LVD ON (LVD Off is also tested ), CSS Disabled, Reset Phase 256 Clock cycle (4096 also tested), PLL disabled.
2. Programming Pins ICCCLK and ICCDATA are pulled high with 2.7K (also tried with 10K) to avoid MCU entering into programming mode and also take care of Noise issues.
3. Software in MCU is such that in the Reset interrupt routine the I/O ports are initialized as outputs and then reset to “False�. The main program has only one instruction “while(1)�.
4. I use C Compiler Panta Ver. 6.0C.2
My observations, when monitored one port pin are:
1. The I/O ports go high undeterministically. Some times only one pin goes high or some time multiple pins go high.
2. Since I have written first statement in the Reset interrupt routine to get the control over the I/O pins, I expect it to take control within calculated 100microSec after reset. But it occurs anytime between 50 to 500 mS(milliSec) after RESET pin going high.
3. I could measure this pulse to be about 100mS.
I think that MCU is failing to call reset interrupt routine immediately after reset. Does any body have solution to this?
MrDBH
[ This message was edited by: mrdbh on 07-02-2005 09:08 ]
[ This message was edited by: mrdbh on 07-02-2005 13:21 ]
