MC68HC08AZ32A Datasheet, PDF (50/312 Pages) Motorola, Inc – HCMOS Microcontroller Unit

Memory
EEDIV[10:0] — EEPROM Timebase Prescaler
These prescaler bits store the value of EEDIV which is used as the divisor to derive a timebase of 35
µs from the selected reference clock source (CGMXCLK or bus block in the CONFIG-2 register) for
the EEPROM related internal timer and circuits. EEDIV[10:0] bits are readable at any time. They are
writable when EELAT = 0 and EEDIVSECD = 1.
The EEDIV value is calculated by the following formula:
EEDIV = INT[Reference Frequency(Hz) x 35 x10^-6 +0.5]
Where the result inside the bracket is rounded down to the nearest integer value
For example, if the reference frequency is 4.9152 MHz, the EEDIV value is 172
NOTE
Programming/erasing the EEPROM with an improper EEDIV value may
result in data lost and reduce endurance of the EEPROM device.
2.7.3.5 EEPROM Timebase Divider Nonvolatile Register
The 16-bit EEPROM timebase divider nonvolatile register consists of two 8-bit registers: EEDIVHNVR
and EEDIVLNVR. The contents of these two registers are respectively loaded into the EEPROM timebase
divider registers, EEDIVH and EEDIVL, after a reset. These two registers are erased and programmed in
the same way as an EEPROM byte.
Address: $FE10
Bit 7
6
5
4
3
2
1
Bit 0
Read: _EEDIVS-
Write: ^ECD
R
R
R
R
EEDIV10 EEDIV9 EEDIV8
Reset:
Unaffected by reset; $FF when blank
R
= Reserved
Figure 2-9. EEPROM Divider Nonvolatile Register High (EEDIVHNVR))
Address:
Read:
Write:
Reset:
$FE11
Bit 7
EEDIV7
6
EEDIV6
5
4
3
2
EEDIV5 EEDIV4 EEDIV3 EEDIV2
Unaffected by reset; $FF when blank
1
EEDIV1
Bit 0
EEDIV0
Figure 2-10. EEPROM Divider Nonvolatile Register Low (EEDIVLNVR)
These two registers are protected from erase and program operations if the EEDIVSECD is set to 1 in the
EEDIVH (see 2.7.3.4 EEPROM Timebase Divider Register) or programmed to a 1 in the EEDIVHNVR.
NOTE
Once EEDIVSECD in the EEDIVHNVR is programmed to 0 and after a
system reset, the EEDIV security feature is permanently enabled because
the EEDIVSECD bit in the EEDIVH is always loaded with 0 thereafter. Once
this security feature is armed, erase and program mode are disabled for
EEDIVHNVR and EEDIVLNVR. Modifications to the EEDIVH and EEDIVL
registers are also disabled. Therefore, care should be taken before
programming a value into the EEDIVHNVR.
MC68HC08AZ32A Data Sheet, Rev. 2
50
Freescale Semiconductor