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COMMUNICATION STOPS WITH THE EZ-USB BOARD

Applies to: uVision Debugger

Answer


Information in this article applies to:


SYMPTOMS

Projects created and debugged on the Cypress EZ-USB board lose monitor communication when single-stepping through the program. Usually this happens after a sequence of instructions similar to the following:

// PORT setup for output
PORTACFG = 0;    // use all port a pins a IO
PORTBCFG = 0;    // use all port b pins a IO
PORTCCFG = 0;    // use all port c pins a IO
OEC = 255;       // and then all as outputs
OEA = 255;       // and then all as outputs
OEB = 255;       // and then all as outputs

CAUSE

The MON51 Target Monitor uses one of the on-chip UART's on the Cypress chip for communication. The UART's transmit and receive lines are part of PORTB or PORTC depending on the serial port.

In the above example, all I/O pins of Port A, Port B, and Port C are set for output (using the OEA, OEB, and OEC SFRs). This causes the serial port to be unable to receive data from the PC.

RESOLUTION

Modify only those pins of Port A, B, and C that do not interfere with the serial port.

MORE INFORMATION

Article last edited on: 2005-01-11 17:16:21

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