AN2156 Freescale Semiconductor / Motorola, AN2156 Datasheet - Page 46

• Manufacturer Part Number: AN2156
• Description: Programming and Erasing FLASH and EEPROM Memories on the MC68HC908AS60A/AZ60A
• Manufacturer: Freescale Semiconductor / Motorola

Application Note
EEPROM Frequently Asked Questions
Question 1
Answer 1
46
NOTE:
These questions and answers are designed to help the user with
frequent concerns.
I cannot program/erase EEPROM memory at all. What should I consider
to make my program/erase code work?
Check the following:
CONFIG-2 is a “write-once” register and has EEDIVCLK = CGMXCLK
out of reset.)
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Freescale Semiconductor, Inc.
For More Information On This Product,
Did you program correct divider values at both EExDIV nonvolatile
high register (EExDIVHNVR) and EExDIV nonvolatile low register
(EExDIVLNVR)?
If you did not program them, did you write correct divider values at
both EExDIV divider high register (EExDIVH) and EExDIV divider
low register (EExDIVL) before executing the erase or program
algorithm operation?
To program and erase the EEPROM, the EEPROM control
requires a constant timebase of 35 s to drive its internal timer. If
proper divider values are not initialized at the divider registers, the
EEPROM erase and/or program operation is not performed
properly. The correct divider value is calculated by the formula in
Configuration Register 2 and EEPROM Timebase Divider
Control
values. One of them is to program the divider value at the
EExDIVHNVR and EExDIVLNVR registers. The other is to write
the value at EExDIVH and EExDIVL registers temporarily before
programming and/or erasing operations.
Did you select a correct EEPROM reference clock source?
The EEPROM reference clock source may be either CGMXCLK or
the system bus clock. The selection of this reference clock source
is defined by the EEDIVCLK bit in the configuration register
(CONFIG-2). The divider value will be changed depending on
which reference clock source you select. Make sure the divider
value is calculated using a correct reference clock speed.
Go to: www.freescale.com
Registers. There are two ways to set correct divider
MOTOROLA
AN2156