Datasheet

MC68HC908QB8 Data Sheet, Rev. 3
Freescale Semiconductor 57
Chapter 5
Configuration Register (CONFIG)
5.1 Introduction
This section describes the configuration registers (CONFIG1 and CONFIG2). The configuration registers
enable or disable the following options:
• Stop mode recovery time (32 × BUSCLKX4 cycles or 4096 × BUSCLKX4 cycles)
•STOP instruction
• Computer operating properly module (COP)
• COP reset period (COPRS): 8176 × BUSCLKX4 or 262,128 × BUSCLKX4
• Low-voltage inhibit (LVI) enable and trip voltage selection
• Auto wakeup timeout period
• Allow clock source to remain enabled in STOP
• Enable IRQ
pin
• Disable IRQ
pin pullup device
• Enable RST
pin
• Clock source selection for the enhanced serial communication interface (ESCI) module
5.2 Functional Description
The configuration registers are used in the initialization of various options. The configuration registers can
be written once after each reset. Most of the configuration register bits are cleared during reset. Since the
various options affect the operation of the microcontroller unit (MCU) it is recommended that this register
be written immediately after reset. The configuration registers are located at $001E and $001F, and may
be read at anytime.
NOTE
The CONFIG registers are one-time writable by the user after each reset.
Upon a reset, the CONFIG registers default to predetermined settings as
shown in Figure 5-1 and Figure 5-2.
Bit 7 6 5 4 3 2 1 Bit 0
Read:
IRQPUD IRQEN R R R ESCIBDSRC OSCENINSTOP RSTEN
Write:
Reset:000 0 0 0 0 U
POR:000 0 0 0 0 0
R
= Reserved U = Unaffected
Figure 5-1. Configuration Register 2 (CONFIG2)