AN1827 Freescale Semiconductor / Motorola, AN1827 Datasheet - Page 22

• Manufacturer Part Number: AN1827
• Description: Programming and Erasing FLASH Memory on the MC68HC908AS60
• Manufacturer: Freescale Semiconductor / Motorola

Application Note
22
Question 2
Answer 2
What is the FLASH charge pump?
The charge pump is a dynamic (clocked) circuit which generates high
voltages internally in the FLASH to program and erase the non-volatile
memory.
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not guarantee FLASH performance if the wrong delay times are
used.
Is the correct FLASH register being written to enable erase or
program?
The MC68HC908AS60 has two FLASH arrays with two separate
sets of control and block protect registers. Make sure the
appropriate register is being addressed. Refer to
Block Protect
Is the maximum pulse value (fls
specification?
Usually, the FLASH will program in fewer than the maximum
specified number of program pulses allowed. However, the
specification is chosen to ensure that even the worst-case
(slowest) bits program by allowing enough programming time.
Setting this value lower than the specification may not work all the
time. Refer to the electrical specifications in MC68HC908AS60
Advance Information, Motorola document order number
MC68HC908AS60/D.
Is the charge pump frequency correct?
The charge pump frequency has to be set between 1.8 MHz and
2.5 MHz. If the bus speed is not between 1.8 MHz and 2.5 MHz,
you must set FDIV bits to generate a suitable charge pump
frequency. Refer to
Is the COP enabled?
If the COP is enabled, make sure that the COP bit is cleared
before the COP reset occurs. Remember that in margin read
mode, every byte requires seven additional cycles for sensing.
Refer to the
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Page Program/Margin Read
Registers.
Charge
Pump.
Pulses
) set correctly according to
Algorithm.
Control and
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