Datasheet

Operating Modes and Resource Mapping
MC68HC812A4 Data Sheet, Rev. 7
60 Freescale Semiconductor
5.4.3 RAM Initialization Register
After reset, addresses of the 1-Kbyte RAM array begin at location $0800 but can be assigned to any
2-Kbyte boundary within the standard 64-Kbyte address space. Mapping of internal RAM is controlled by
five bits in the INITRM register. The RAM array occupies the last 1 Kbyte of the 2-Kbyte block.
Read: Anytime
Write: Once in normal modes; anytime in special modes
RAM15–RAM11 — RAM Position Bits
These bits specify the upper five bits of the 16-bit RAM address.
5.4.4 EEPROM Initialization Register
The MCU has 4 Kbytes of EEPROM which is activated by the EEON bit in the INITEE register.
Mapping of internal EEPROM is controlled by four bits in the INITEE register. After reset, EEPROM
address space begins at location $1000 but can be mapped to any 4-Kbyte boundary within the standard
64-Kbyte address space.
Read: Anytime
Write: Varies from bit to bit
EE15–EE12 — EEPROM Position Bits
These bits specify the upper four bits of the 16-bit EEPROM address.
Normal modes: Write once
Special modes: Write anytime
EEON — EEPROM On Bit
EEON enables the on-chip EEPROM. EEON is forced to 1 in single-chip modes.
Write anytime
1 = EEPROM at address selected by EE15–EE12
0 = EEPROM removed from memory map
Address: $0010
Bit 7654321Bit 0
Read:
RAM15 RAM14 RAM13 RAM12 RAM11 0 0 0
Write:
Reset:00001000
Figure 5-3. RAM Initialization Register (INITRM)
Address: $0012
Bit 7654321Bit 0
Read:
EE15 EE14 EE13 EE12 0 0 0 EEON
Write:
Reset:
Expanded and peripheral:00010001
Single-chip:11110001
Figure 5-4. EEPROM Initialization Register (INITEE)