MC68711E20CFNE3 Datasheet, PDF (55/242 Pages) –

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
STAB
JSR
CLR
#$16
$103B
0,X
#$17
$103B
DLY10
$103B
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
EEPROM
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 Chapter 11 Ordering Information and Mechanical
Specifications for the exact part number.
For further information, these engineering bulletins have been included at the back of this data book:
• EB183 — Enabling the Security Feature on the MC68HC711E9 Devices with PCbug11 on the
M68HC711E9PGMR
• EB188 — Enabling the Security Feature on M68HC811E2 Devices with PCbug11 on the
M68HC711E9PGMR
M68HC11E Family Data Sheet, Rev. 5.1
Freescale Semiconductor
55