User manual

Troubleshooting
© 2006 Microchip Technology Inc. DS51464C-page 113
B.6 ERROR MESSAGES – PC
These are some error messages you may receive:
• Could Not Open the Communications Port
• USB Communication Could Not Be Established
• Device is Code-Protected
• Parity Error Found in Program Memory
• Program Memory Contains Code-Protected Data
• Invalid Checksum
B.6.1 Could Not Open the Communications Port
If the communications port cannot be opened, it is either because another application
has opened the port, or the port does not exist. Make sure the port number is valid and
that no other application is using it, such as another instance of MPLAB IDE.
B.6.2 USB Communication Could Not Be Established
If, while MPLAB PM3 is enabled using USB, the MPLAB PM3 unit is powered off and
on quickly or power is temporarily interrupted, to reestablish USB communications, you
must:
• Make sure the MPLAB PM3 power switch is off.
• Deselect MPLAB PM3 as the current programmer (Programmer>Select
Programmer>None).
• Turn the MPLAB PM3 power back on.
• Reselect MPLAB PM3 as the programmer (Programmer>Select Programmer>
MPLAB PM3).
• Enable the MPLAB PM3 programmer (Programmer>Enable Programmer
). Wait
10 seconds for Windows to recognize it. If it doesn’t work, restart the PC or try
connecting to a different USB root hub.
B.6.3 Device is Code-Protected
If you attempt to read a code-protected device, you will get this warning. Obtain the
original hex code from a file or a non-protected device. Also see
Section B.6.5 “Program Memory Contains Code-Protected Data”.
B.6.4 Parity Error Found in Program Memory
Several devices have a Configuration bit to request the calculation of parity. When the
bit is set to “ON,” the contents of the program memory are compared and assigned
“even” or “odd” parity. When set to “OFF,” the device does not perform a comparison.
On a blank device, the parity Configuration bit is set to “ON” by default. If the device is
programmed with the parity Configuration bit set to “ON,” any reprogramming of the
device may result in a parity error being displayed. This occurs because a mismatch
has been detected between the current parity and the parity last programmed.
Receiving a parity error, however, does not stop the device from being programmed.
However, if the device is programmed with the parity bit set to “OFF,” no comparison of
the program memory contents for parity will take place. The device can be
reprogrammed without receiving a message regarding parity.
All OTP devices, including those that have the parity Configuration bit, cannot
successfully reprogram any bit value of ‘0’ to a ‘1’. If a device has been programmed
with the parity Configuration bit set to “OFF,” the parity checking cannot be turned back
to “ON.” A blank device will have to be used.