mc68hc916y3 Freescale Semiconductor, Inc, mc68hc916y3 Datasheet - Page 194

• Manufacturer Part Number: mc68hc916y3
• Description: Mc68hc16y3 16 Bit Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

8.2 Flash EEPROM Array
8.3 Flash EEPROM Operation
8.3.1 Reset Operation
8-2
MOTOROLA
Four additional flash EEPROM words in the control block can contain bootstrap infor-
mation for use during reset. Control registers are located in supervisor data space. Re-
fer to D.5 Flash EEPROM Modulefor register and bit field information.
The control register blocks for the 16-, 48-, and 32-Kbyte flash EEPROM modules start
at locations $YFF800, $YFF820, and $YFF840 respectively. The following register de-
scriptions apply to the corresponding register in all control blocks. References to FE-
ExMCR, for example, apply to FEE1MCR (in the 16-Kbyte module), FEE2MCR (in the
48-Kbyte module), and FEE3MCR (in the 32-Kbyte module).
A number of control register bits have associated bits in “shadow” registers. The val-
ues of the shadow bits determine the reset states of the control register bits. Shadow
registers are programmed or erased in the same manner as a location in the array,
using the address of the corresponding control registers.When a shadow register is
programmed, the data is not written to the corresponding control register. The new
data is not copied into the control register until the next reset. The contents of shadow
registers are erased when the array is erased.
Configuration information is specified and programmed independently of the array. Af-
ter reset, registers in the control block that contain writable bits can be modified. Writes
to these registers do not affect the associated shadow register. Certain registers can
be written only when LOCK = 0 or STOP = 1 in FEExMCR.
The base address registers specify the starting address of the flash EEPROM array.
The user programs the reset base address. The base address of the 16-Kbyte array
must be on a 16-Kbyte boundary; the base address of the 48-Kbyte array must be on
a 48-Kbyte boundary; the base address of the 32-Kbyte array must be on a 32-Kbyte
boundary. Behavior will be indeterminate if one flash EEPROM array overlaps the
other.
The base address must also be set so that an array does not overlap a flash EEPROM
control block in the data space memory map. If an array does overlap a control block,
accesses to the 32 bytes in the array that is overlapped are ignored, allowing the flash
EEPROM control blocks to remain accessible. If the array overlaps the control block
of another module, the results will be indeterminate.
The following paragraphs describe the operation of the flash EEPROM module during
reset, system boot, normal operation, and while it is being programmed or erased.
Reset initializes all registers to certain default values. Some of these reset values are
programmable by the user and are contained in flash EEPROM shadow registers.
Freescale Semiconductor, Inc.
For More Information On This Product,
FLASH EEPROM MODULE
Go to: www.freescale.com
MC68HC16Y3/916Y3
USER’S MANUAL