MOTOROLA MC68HC11K series

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 actual EEPROM byte. When programming the CONFIG register,
the  EEPROM  byte  is  being accessed. When the CONFIG register is
being read, the static latches are being 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 cannot
be  read  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 reset.

bit7:  ROMAD - ROM/EPROM Mapping Control
In single-chip mode ROMAD is forced to one out of reset.
0 = ROM/EPROM located at $2000-$7FFF ($2000-$9FFF in MC68HC11KA2)
1 = ROM/EPROM located at $A000-$FFFF ($8000-$FFFF in MC68HC11KA2)

Bit6 - Not implemented
Always reads one


bit5: CLKX - XOUT Clock Enable
0 = XOUT pin disabled
1 = x clock driven out on the XOUT pin

bit4: PAREN - Pull-Up Assignment Register Enable
Refer to 6 Parallel Input/Output.

bit3: NOSEC - Security Disable
NOSEC is invalid unless the security mask option is specified before the 
MCU is manufactured. If security mask option is omitted NOSEC always reads one.
0 = Security enabled
1 = Security disabled

bit2: NOCOP - COP System Disable
Resets to programmed value
0 = COP enabled (forces reset on time-out)
1 = COP disabled (does not force reset on time-out)

bit1: ROMON - ROM/EPROM Enable
In single-chip mode, ROMON is forced to one out of reset. In special test 
mode, ROMON is forced to
zero out of reset.
0 = ROM/EPROM removed from memory map
1 = ROM/EPROM present in memory map

bit0: EEON - EEPROM Enable
0 = EEPROM disabled from memory map
1 = EEPROM present in memory map with location depending on 
value specified in EE[3:0] in INIT2

При записи CONFIG значение меняется только после ребута.