AN1827 Freescale Semiconductor / Motorola, AN1827 Datasheet - Page 11

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

Block Protection
Erase Operation
AN1827
MOTOROLA
NOTE:
To protect the contents in the FLASH array from being inadvertently
programmed or erased by run-away code in the user application, the
FLASH block protect register option was implemented. This register is
composed of two non-volatile bytes within the FLASH-1 array, with one
byte per FLASH array. Once the block protect bits are set in the FLBPR
registers, the defined address ranges are protected from being
programmed or erased. See
a description of address ranges.
The FLBPR register itself can be erased or programmed only with an
external voltage V
V
additional measure to prevent inadvertent programming or erasing of
FLASH contents in an application.
To implement in-system program or erase for a protected area of
FLASH, a high voltage signal must be routed to the IRQ pin.
To erase a FLASH array, follow this 9-step procedure.
a flowchart of this procedure.
DD
1. Set ERASE = 1, and set the BLK bits and FDIV bits.
2. Read the FLASH block protect register.
Freescale Semiconductor, Inc.
+ 2 V and V
For More Information On This Product,
ERASE = 1 configures the FLASH memory for an erase operation.
The BLK bits determine the erase block size: whole array, half
array, 512 bytes or 64 bytes. The FDIV bits determine the charge
pump frequency. The frequency should be selected within the
range between 1.8 MHz and 2.5 MHz. Refer to
The block protect registers must be read before high voltage can
be enabled. If the desired address set in step 3 is in a protected
block, erase will fail.
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DD
HI
+ 4 V. Use of the block protect register is an
on the IRQ pin. V
Control and Block Protect Registers
HI
is defined as a voltage between
Charge
Figure 3
Application Note
Block Protection
Pump.
shows
for
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