AN1836 Motorola / Freescale Semiconductor, AN1836 Datasheet - Page 29

• Manufacturer Part Number: AN1836
• Description: FLASH Programming for Motorola MC68HC912 Microcontrollers
• Manufacturer: Motorola / Freescale Semiconductor

Testing
for Marginally
Programmed
FLASH
AN1836
MOTOROLA
fall more than .35 volts below V
latchup conditions or even damage to the V
result in improper programming, reduced current capability on the V
pin, or other types of damage to the V
Also important to remember is that during power-up or power-down,
when V
unknown state, and it might cause the voltage on the V
applied to the array inadvertently, causing data disturbance in the
FLASH array.
Some customers return devices claiming defective memory cells, since
the .s19 files won’t verify because of bits that don’t seem to be
programmed or that seem to change state after a good deal of time has
passed after programming. Generally, these returns are caused by
inadequately programmed FLASH cells. This can be due to improper
programming routines which do not meet the requirements of Motorola’s
programming algorithm or inadequate programming voltage power
supplies. However, if the programming algorithms and power supply
requirements outlined in this application note are adhered to, marginal
programming should not be a concern.
Marginally programmed devices would, by their very nature, tend to
allow bitcells to change state over time, since only enough charge was
transferred to allow the cell to read properly immediately after
programming. If these bit flipping symptoms are experienced, there are
methods to help determine if devices are not being adequately
programmed.
If there is a reason to believe that some devices might be marginally
programmed, a simple test can be run to determine whether the FLASH
is strongly or marginally programmed. The method is not exact, but it can
be effective in detecting marginally programmed parts, relative to
strongly programmed ones. Most importantly, this test should be used to
help identify insufficient programming voltage supply designs.
Contact a salesperson or field applications engineering representative to
determine if these testing methods are appropriate to your situation.
DD
is below 4.5 volts, the MCU logic could potentially be in an
DD
Other FLASH Hardware Device Considerations
at any time, it can lead to pad-driven
FP
pin.
FP
input pad. This could
FP
Application Note
pin to be
FP
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