
Operating Modes and On-Chip Memory
EEPROM
M68HC11E Family — Rev. 5
Data Sheet
MOTOROLA
Operating Modes and On-Chip Memory
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2.5.1.5  EEPROM Byte Erase 
This is an example of how to erase a single byte of EEPROM. 
BYTEE 
LDAB
STAB
STAB
LDAB
#$16
$103B
0,X
#$17
BYTE = 1, ERASE = 1, EELAT = 1 
Set to BYTE erase mode 
Write any data to address to be erased 
BYTE = 1, ERASE = 1, EELAT = 1, 
EPGM = 1 
Turn on high voltage 
Delay 10 ms 
Turn off high voltage and set 
to READ mode 
STAB
JSR
CLR
$103B
DLY10
$103B
2.5.1.6  CONFIG Register Programming 
Because the CONFIG register is implemented with EEPROM cells, use EEPROM 
procedures to erase and program this register. The procedure for programming is 
the same as for programming a byte in the EEPROM array, except that the 
CONFIG register address is used. CONFIG can be programmed or erased 
(including byte erase) while the MCU is operating in any mode, provided that 
PTCON in BPROT is clear. 
To change the value in the CONFIG register, complete this procedure. 
1.
Erase the CONFIG register. 
2.
Program the new value to the CONFIG address. 
3.
Initiate reset. 
NOTE:
Do not initiate a reset until the procedure is complete.
2.5.2  EEPROM Security 
The optional security feature, available only on ROM-based MCUs, protects the 
EEPROM and RAM contents from unauthorized access. A program, or a key 
portion of a program, can be protected against unauthorized duplication. To 
accomplish this, the protection mechanism restricts operation of protected devices 
to the single-chip modes. This prevents the memory locations from being 
monitored externally because single-chip modes do not allow visibility of the 
internal address and data buses. Resident programs, however, have unlimited 
access to the internal EEPROM and RAM and can read, write, or transfer the 
contents of these memories. 
An enhanced security feature which protects EPROM contents, RAM, and 
EEPROM from unauthorized accesses is available in MC68S711E9. Refer to 
Section 11. Ordering Information and Mechanical Specifications
 for the exact 
part number. 
F
Freescale Semiconductor, Inc.
n
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