User`s manual

Rabbit 4000 Designer’s Handbook rabbit.com 81
11. Troubleshooting Tips for New
Rabbit-Based Systems
If the Rabbit design conventions were followed and Dynamic C cannot establish target communications
with the Rabbit 4000-based system, there are a number of initial checks and some diagnostic tests that can
help isolate the problem.
11.1 Initial Checks
Perform the first two checks with the /RESET line tied to ground.
1. With a voltmeter check for VDDIO, VDDINT, VBAT and VBATIO for the correct voltages. Also
check VSSIO and VSSINT for proper connection to ground.
2. With an oscilloscope check the 32.768 kHz oscillator on CLK32K (pin 49). Make sure that it is oscillat-
ing and that the frequency is correct.
3. With an oscilloscope check the main system oscillator by observing the signal CLK. With the reset held
high and no existing program in the flash memory attached to the processor, this signal should have a
frequency one eighth of the main crystal or oscillator frequency.
11.2 Diagnostic Tests
The cold boot mode may be used to communicate with the target system without using Dynamic C. As dis-
cussed in Section 4.1, in cold boot mode triplets may be received by serial port A or the slave port. To load
and run the diagnostic programs, the easiest method is to use the programming cable and a specialized ter-
minal emulator program over asynchronous serial port A. To use the slave port requires more setup than
the serial port method and it is not considered here. Since each board design is unique, it is not possible to
give a one-size-fits-all solution for diagnosing board problems. However, using the cold boot mode allows
a high degree of flexibility. Any sequence of triplets may be sent to the target.
11.2.1 Program to Transmit Diagnostic Tests
The file SerialIO_1.zip is available for download at:
http://ftp1.digi.com/support/driver/rabbit_serial_io.zip
The zip file contains the specialized terminal emulator program serialIO.exe and several diagnostic
programs. The diagnostic programs test a variety of functionality, and allow the user to simulate some of
the behavior of the Dynamic C download process.