MC68HC05B6_13 Datasheet, PDF (45/302 Pages) Freescale Semiconductor, Inc – Microcontrollers

3.5
EEPROM
The user EEPROM consists of 256 bytes of memory located from address $0100 to $01FF. 255
bytes are general purpose and 1 byte is used by the option register. The non-volatile EEPROM is
byte erasable.
An internal charge pump provides the EEPROM voltage (V_PP1), which removes the need to supply
3
a high voltage for erase and programming functions. The charge pump is a capacitor/diode ladder
network which will give a very high impedance output of around 20-30 MΩ. The voltage of the
charge pump is visible at the VPP1 pin. During normal operation of the device, where
programming/erasing of the EEPROM array will occur, VPP1 should never be connected to either
VDD or VSS as this could prevent the charge pump reaching the necessary programming voltage.
Where it is considered dangerous to leave VPP1 unconnected for reasons of excessive noise in
a system, it may be tied to V_DD; this will protect the EEPROM data but will also increase power
consumption, and therefore it is recommended that the protect bit function is used for regular
protection of EEPROM data (see Section 3.5.5).
In order to achieve a higher degree of security for stored data, there is no capability for bulk or row
erase operations.
The EEPROM control register ($0007) provides control of the EEPROM programming and erase
operations.
Warning: The VPP1 pin should never be connected to VSS, as this could cause permanent
damage to the device.
3.5.1 EEPROM control register
EEPROM/ECLK control
Address bit 7
bit 6
bit 5
bit 4
bit 3
bit 2
bit 1
bit 0
State
on reset
$0007 0
0
0
0 ECLK E1ERA E1LAT E1PGM 0000 0000
ECLK
See Section 4.3 for a description of this bit.
E1ERA — EEPROM erase/programming bit
Providing the E1LAT and E1PGM bits are at logic one, this bit indicates whether the access to the
EEPROM is for erasing or programming purposes.
1 (set) – An erase operation will take place.
0 (clear) – A programming operation will take place.
Once the program/erase EEPROM address has been selected, E1ERA cannot be changed.
MC68HC05B6
Rev. 4.1
MEMORY AND REGISTERS
Freescale
3-3