MC68HC08AS32A Datasheet, PDF (41/296 Pages) Motorola, Inc – Microcontrollers

Freescale Semiconductor, Inc.
Memory
Electrically Erasable Programmable ROM (EEPROM)
• On-chip charge pump for programming/erasing
• Program/erase protection option
• AUTO bit driven programming/erasing time feature
2.5.1 Functional Description
The 512 bytes of EEPROM are located at $0800–$09FF and can be programmed
or erased without an additional external high voltage supply. The program and
erase operations are enabled through the use of an internal charge pump. An
internal state machine controls the program and erase timing. For each byte of
EEPROM, the write/erase endurance is 10,000 cycles.
2.5.1.1 EEPROM Configuration
The 8-bit EEPROM non-volatile register (EENVR) and the 16-bit EEPROM
timebase divider non-volatile register (EEDIVNVR) contain the default settings for
the following EEPROM configurations:
• EEPROM timebase reference
• EEPROM program/erase protection
• EEPROM block protection
EENVR and EEDIVNR are non-volatile EEPROM registers. They are programmed
and erased in the same way as EEPROM bytes. The contents of these registers
are loaded into their respective volatile registers during a MCU reset. The values
in these read/write volatile registers define the EEPROM configurations.
For EENVR, the corresponding volatile register is the EEPROM array configuration
register (EEACR). For the EEDIVNVR (two 8-bit registers: EEDIVHNVR and
EEDIVLNVR), the corresponding volatile register is the EEPROM divider register
(EEDIV: EEDIVH and EEDIVL).
2.5.1.2 EEPROM Timebase Requirements
A 35 µs timebase is required by the EEPROM control circuit for program and erase
of EEPROM content. This timebase is derived from dividing the CGMXCLK or bus
clock (selected by EEDIVCLK bit in mask option register B) using a timebase
divider circuit controlled by the 16-bit EEPROM timebase divider EEDIV register
(EEDIVH and EEDIVL).
As the CGMXCLK or bus clock is user selected, the EEPROM timebase divider
register must be configured with the appropriate value to obtain the 35 µs. The
timebase divider value is calculated by using the following formula:
EEDIV = INT [Reference Frequency (Hz) x 35 x 10^–6 + 0.5]
This value is written to the EEPROM timebase divider register (EEDIVH and
EEDIVL) or programmed into the EEPROM timebase divider non-volatile register
MC68HC08AS32A — Rev. 1
MOTOROLA
Memory
For More Information On This Product,
Go to: www.freescale.com
Data Sheet
41