Operating Modes
Internal Resource Mapping
68HC(9)12DG128 Rev 1.0
MOTOROLA
Operating Modes
69
11-modes
Flash EEPROM
mapping through
internal Memory
Expansion
The Page Index register or PPAGE provides memory management for
the 68HC(9)12DG128. PPAGE consists of three bits to indicate which
physical location is active within the windows of the 68HC(9)12DG128.
The 68HC(9)12DG128 has a user’s program space window, a register
space window for Flash module registers (68HC912DG128 only), and a
test program space window.
The user’s program page window consists of 16K Flash EEPROM bytes
(68HC912DG128) or ROM bytes (68HC12DG128). One of eight pages
is viewed through this window for a total of 128K accessible Flash
EEPROM bytes.
On the 68HC912DG128, the register space window consists of a 4-byte
register block. One of four pages is viewed through this window for each
of the 32K flash module register blocks of 68HC912DG128.
The test mode program page window consists of 32K Flash EEPROM
bytes (68HC912DG128) or ROM bytes (68HC12DG128). One of the
four 32K byte arrays is viewed through this window for a total 128K
accessible Flash EEPROM bytes (68HC912DG128) or ROM bytes
(68HC12DG128). This window is only available in special mode for test
purposes and replaces the user’s program page window.
68HC(9)12DG128 has a five pin port, Port K, for emulation and for
general purpose I/O. Three pins are used to emulate the three page
indices (PPAGE bits) and one pin is used as an emulation chip select.
When these four pins are not used for emulation they serve as general
purpose I/O pins. The fifth Port K pin is used as a general purpose I/O
pin.
Program space
expansion
There are 128K bytes of Flash EEPROM (68HC912DG128) or ROM
(68HC12DG128). With a 64K byte address space, the PPAGE register
is needed to perform on-chip memory expansion. A program space
window of 16K byte pages is located from $8000 to $BFFF. Three page