EEPROM
M68HC11E Family Data Sheet, Rev. 5.1
Freescale Semiconductor
55
2.5.1.5 EEPROM Byte Erase
This is an example of how to erase a single byte of EEPROM.
BYTEE
LDAB
#$16
BYTE = 1, ERASE = 1, EELAT = 1
STAB
$103B
Set to BYTE erase mode
STAB
0,X
Write any data to address to be erased
LDAB
#$17
BYTE = 1, ERASE = 1, EELAT = 1,
EPGM = 1
STAB
$103B
Turn on high voltage
JSR
DLY10
Delay 10 ms
CLR
$103B
Turn off high voltage and set
to READ mode
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
For further information, these engineering bulletins have been included at the back of this data book: