Freescale Semiconductor, Inc.
Operating Modes and On-Chip Memory
3.6.3 CONFIG register programming
Because the CONFIG register is implemented with EEPROM cells, use
EEPROM procedures to erase and program this register. The procedure
for programming is the same as for programming a byte in the EEPROM
array, except that the CONFIG register address is used. CONFIG can be
programmed or erased (including byte erase) while the MCU is
operating in any mode, provided that PTCON in BPROT is clear. To
change the value in the CONFIG register, complete the following
procedure. Do not initiate a reset until the procedure is complete.
1. Erase the CONFIG register.
2. Program the new value to the CONFIG address.
3. Initiate reset.
CONFIG — System configuration register
State
Address bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0
on reset
ROMA
D
PARE NOSE NOCO ROMO
Configuration control (CONFIG) $003F
1
1
EEON x11x 1xxx
N
C
P
N
For a description of the bits contained in the CONFIG register refer to
CONFIG — System configuration register.
CONFIG is made up of EEPROM cells and static working latches. The
operation of the MCU is controlled directly by these latches and not the
EEPROM byte. When programming the CONFIG register, the EEPROM
byte is accessed. When the CONFIG register is read, the static latches
are accessed.
These bits can be read at any time. The value read is the one latched
into the register from the EEPROM cells during the last reset sequence.
A new value programmed into this register is not readable until after a
subsequent reset sequence. Unused bits always read as ones.
If SMOD = 1, CONFIG bits can be written at any time. If SMOD = 0,
CONFIG bits can only be written using the EEPROM programming
sequence, and are neither readable nor active until latched via the next
Technical Data
MC68HC11P2 — Rev 1.0
Operating Modes and On-Chip Memory
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