The MC68HC11PA8/PB8 are members of the M68HC11 family of HCMOS
microcontrollers. In addition to 48K bytes of ROM, contains
2K bytes of RAM and 512 bytes of EEPROM.
Wide range of serial communications; in addition to an SCI subsystem, 
the device contains an SPI subsystem and an I2C+ serial interface
8-bit analog to digital (A/D) converter.
Up to 39 general-purpose I/O lines plus up to 6 input-only lines.


CONFIG - System configuration register    $003F
bit7  bit6  bit5  bit4  bit3  bit2  bit1  bit0
ROMAD MBSP CLK4X PAREN NOSEC NOCOP ROMON  EEON

ROMAD - ROM mapping control
1 (set) - ROM/EPROM addressed from $4000 to $FFFF.
0 (clear) - ROM/EPROM addressed from $0000 to $BFFF (expanded mode only).
In single chip mode, reset sets this bit.

MBSP - Synchronous serial interface select
1 (set) - SPI is disabled. The I2C bus, if enabled, uses port D[4, 3] pins.
0 (clear) - If enabled, the I2C bus uses port E[7, 6] pins.

CLK4X - 4X clock enable+
1 (set) - 4XCLK or EXTALi driven out on the XOUT pin (see Section 4.3.2.5)
0 (clear) - XOUT pin disabled.

PAREN - Pull-up assignment register enable (refer to Section 6)
1 (set) - Pull-ups can be enabled using PPAR.
0 (clear) - All pull-ups disabled (not controlled by PPAR).

NOSEC - EEPROM security disabled (refer to Section 4.4.4)
1 (set) - Disable security.
0 (clear) - Enable security.

NOCOP - COP system disable (refer to Section 5)
1 (set) - COP system disabled.
0 (clear) - COP system enabled (forces reset on timeout).

ROMON - ROM enable
1 (set) - ROM/EPROM included in the memory map.
0 (clear) - ROM/EPROM excluded from the memory map.
In single chip mode, reset sets this bit. In special test mode, reset clears ROMON.

EEON - EEPROM enable
1 (set) - EEPROM included in the memory map.
0 (clear) - EEPROM is excluded from the memory map

При записи CONFIG значение меняется только после ребута.