MC908JL8CDWE Datasheet, PDF (41/212 Pages) Freescale Semiconductor, Inc – Microcontrollers

Chapter 3
Configuration and Mask Option Registers (CONFIG & MOR)
3.1 Introduction
This section describes the configuration registers, CONFIG1 and CONFIG2; and the mask option register
(MOR).
The configuration registers enable or disable these options:
• Computer operating properly module (COP)
• COP timeout period (2¹³â€“2⁴ or 2¹⁸–2⁴ ICLK cycles)
• Internal oscillator during stop mode
• Low voltage inhibit (LVI) module
• LVI module voltage trip point selection
• STOP instruction
• Stop mode recovery time (32 or 4096 ICLK cycles)
• Pull-up on IRQ pin
The mask option register selects the oscillator option:
• Crystal or RC
3.2 Functional Description
The configuration registers are used in the initialization of various options. The configuration registers can
be written once after each reset. All of the configuration register bits are cleared during reset. Since the
various options affect the operation of the MCU, it is recommended that these registers be written
immediately after reset. The configuration registers are located at $001E and $001F. The configuration
registers may be read at anytime.
NOTE
The options except LVIT[1:0] are one-time writable by the user after each
reset. The LVIT[1:0] bits are one-time writable by the user only after each
POR (power-on reset). The CONFIG registers are not in the FLASH
memory but are special registers containing one-time writable latches after
each reset. Upon a reset, the CONFIG registers default to predetermined
settings as shown in Figure 3-1 and Figure 3-2.
The mask option register (MOR) is used to select the oscillator option for the MCU: crystal oscillator or
RC oscillator. The MOR is implemented as a byte in FLASH memory. Hence, writing to the MOR requires
programming the byte.
MC68HC908JL8/JK8 • MC68HC08JL8/JK8 • MC68HC908KL8 Data Sheet, Rev. 3.1
Freescale Semiconductor
41