mc9s08ac16 Freescale Semiconductor, Inc, mc9s08ac16 Datasheet - Page 43

• Manufacturer Part Number: mc9s08ac16
• Description: Hcs08 Microcontrollers 8-bit Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

4.2
The registers in the MC9S08AC16 Series are divided into these three groups:
Direct-page registers can be accessed with efficient direct addressing mode instructions. Bit manipulation
instructions can be used to access any bit in any direct-page register.
user-accessible direct-page registers and control bits.
The direct page registers in
requires the lower byte of the address. Because of this, the lower byte of the address in column one is
shown in bold text. In
Table
from the bit names to the right. Cells that are not associated with named bits are shaded. A shaded cell with
a 0 indicates this unused bit always reads as a 0. Shaded cells with dashes indicate unused or reserved bit
locations that could read as 1s or 0s.
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4-2,
Direct-page registers are located in the first 112 locations in the memory map, so they are
accessible with efficient direct addressing mode instructions.
High-page registers are used much less often, so they are located above 0x1800 in the memory
map. This leaves more room in the direct page for more frequently used registers and variables.
The nonvolatile register area consists of a block of 16 locations in FLASH memory at
0xFFB0–0xFFBF.
Nonvolatile register locations include:
— Three values which are loaded into working registers at reset
— An 8-byte backdoor comparison key which optionally allows a user to gain controlled access
Register Addresses and Bit Assignments
Table
to secure memory
Because the nonvolatile register locations are FLASH memory, they must be erased and
programmed like other FLASH memory locations.
4-3, and
Table 4-3
Table
Table 4-2
4-4, the register names in column two are shown in bold to set them apart
and
MC9S08AC16 Series Data Sheet, Rev. 0
Table 4-4
can use the more efficient direct addressing mode which only
PRELIMINARY
the whole address in column one is shown in bold. In
Table 4-2
is a summary of all
Chapter 4 Memory
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