5.
NEEDS CAL With Both Error Registers = $00
There are three error cases in which NEEDS CAL is displayed on the LCD screen
but no error is indicated in either the Historical Master Error Register or the
Historical Slave Error Register. They are as follows:
5.1
Unit Not Calibrated - $00 / 00000000
5.1.1
Description:
This error occurs when the proper calibration signature $fa $ce is not written in
EEPROM locations $2e and $2f respectively.
5.1.2
Suggestions:
• Verify that $fa $ce is indeed at locations $2e and $2f
• Calibrate the unit, power down, then re-test.
5.2
Slave Communications Error - $00 / 00000000
5.2.1
Description:
This error occurs when the Slave doesn’t respond to the Master’s commands
within a pre-defined time period.
5.2.2
Suggestions:
• Verify that the Slave and Master microcontrollers are properly installed by
powering down and then powering up.
• Verify that both microcontrollers’ pins all make good electrical contact to the
PCB.
5.3
I2C Bus Error - $00 / 00000000
5.3.1
Description:
The I2C bus is a two wire communication link between the Slave, Master, and
EEPROM. Although the Slave and Master don’t talk to each other directly using
this bus, they do use it to communicate with the EEPROM. All data stored in and
retrieved from EEPROM passes through this bus. The voltage levels on the two
bus lines indicate different things to the microcontrollers. In addition, if both the
Master and the Slave try to use the bus at the same time, and error could occur.
5.3.2
Suggestions:
• With the unit powered up check the voltage levels of TP5 and TP6. They
should be 5V. If one of them is “stuck” at some other voltage check
for broken traces or shorts involving that particular circuit.
• Historically we have found that this error can be resolved by merely clearing
the error registers, powering the unit down, and then powering it back on.
