68HC908JB8 monitor mode problem

I try to send JB8 hex FF FF FF FF FF FF FF FF BUT I got nothing echoed

snipped-for-privacy@yahoo.com wrote:

Your phrasing is unclear here. I am assuming that you mean that you could not get the P&E software to connect to the target again instead of the implied meaning above that you couldn't find the P&E software on your developement machine. :-)

As I have never used the P&E programmer (I wrote my own because I wanted to develop under Linux), my comments below are restricted to what the JB8 itself requires and does not cover any additional requirements that may be required by the P&E programmer.

First off, the 8 volt IRQ seems a little low; I typically see 9 volts on my programming circuit. Since you appear to have built your programming circuit, have you followed the design as specified in the JB8 datasheet ? Note the use of the Zener diode to control the maximum voltage seen on the IRQ pin.

The high voltage on the IRQ pin is only one of the monitor mode entry requirements. You also need to pull-up and pull-down various pins as specified in the datasheet.

As for why you were able to program it for the first time, (I'm assuming that it was a blank JB8 that you started with), the JB8 automatically enters monitor mode if the reset vector is blank without requiring the conditions specified above. You can also find this mentioned in the datasheet.

Once the reset vector is programmed, you _must_ follow the monitor entry conditions as specified in the datasheet.

Note also that the security code that you use to enter monitor mode varies depending on what you have programmed into the vectors preceeding the reset vector.

If you fail security, you get 0xAD back from the flash memory areas, but can still force a mass erase to reset everything, including the vectors, back to 0xff. How you do this depends on your programmer.

HTH,

Simon.

Yep, I've followed the design as specified in the JB8 datasheet, the only difference is I use a MAX232A. It can handle blank chips, the hardware should be okay.

I've checked the echo timing: the echo for security check is mixed in the transmitted data. The programmer I am using can detect echo from blank chip, but failed to detect from writtened chip.

I am using a serial port tx/rx software to check echo.

I am still confused about the hex command said in the datasheet. What's the syntax for those command? Freescale only listed the header info. for those command like "read" = "0x49", but how to add address to it? How to call the mass erase routine in Hex format?

thanks for replied.

Sim> > > Hi, here is a newbie to this chip.

On Dec 14, 11:39 pm, snipped-for-privacy@yahoo.com wrote: ...

...

The main problem I have had in the past with entering monitor mode is that you have to power down the device first and I mean really power it down to a couple of tenths of a volt. In one case I had to put a resistor across the power rails to bring the voltage down in a reasonable time or the decouplers would keep the device powered enough for several seconds to keep it secure.

kevin

It looks like you are referring to the monitor mode commands like IREAD (0x1a) and IWRITE (0x19).

If so, you should only need those when you are writing your own programmer. (BTW, READ is 0x4a not 0x49, WRITE is 0x49.)

I can only suggest that you recheck your programming circuit throughly, focusing on the parts that are required for forced monitor entry.

Since you appear to have programmed it successfully the first time, it sounds like your circuit may not be meeting the JB8's requirements in this area.

A possible alternative suggestion is that you have programmed some vectors other than the reset vector and hence the security code may have changed.

Simon.

I found something wrong unusual in my project. The circuits I built is the same like the reference design as follows:

schematic is here:

I am using 20-pin DIP instead of the 28-pin SOIC . I leaved all pins for sensing input/output as blank. I used one set of RX/TX in MAX232A. I replaced the BAT schottky by an 1N4006.

But the problem is, in the reference design book, I copied and programmed the source code into the 20-pin DIP, in those codes some pins were used only for SOIC-28, the databook said all pins exist but unconnected in the less pins package, e.g. 20 pinpackage.

And I verified at $FFF6-FFFD is E1-6B-E1-6B-E1-1C-E1-6B. After I connected the /IRQ to 8.05 volts, press button to let /RST=0 once, the chip still entered "user mode." I could identify the USB device and controlled device through USB. As the reference design said, after /IRQ=Vdd+Vhi, the USB device couldn't be recognized by computer and entered monitor mode, but for my circuits, it was recognized by the computer and still worked in user mode.

Is't possible to do programming/erasing under user mode? it seems impossible.

Sim> > > Yep, I've followed the design as specified in the JB8 datasheet, the

Did you leave in the pull-up and pull-down connections for entering monitor mode (and using the appropriate component values) as documented in the datasheet ?

If you did, then your next stop should be the Freescale forums located at

Simon.

I found a guy met same problem, and I tried all the way he had tried, jee, here is the link

I have no idea...I even tried to put 10 volt to /IRQ, nothing happened.

Sim> > > I found something wrong unusual in my project.