Freescale Semiconductor MC68HC908MR32 - Manual (Page 73)

MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor 73
Chapter 5
Configuration Register (CONFIG)
5.1 Introduction
This section describes the configuration register (CONFIG). This register contains bits that configure
these options:
• Resets caused by the low-voltage inhibit (LVI) module
• Power to the LVI module
• Computer operating properly (COP) module
• Top-side pulse-width modulator (PWM) polarity
• Bottom-side PWM polarity
• Edge-aligned versus center-aligned PWMs
• Six independent PWMs versus three complementary PWM pairs
5.2 Functional Description
The configuration register (CONFIG) is used in the initialization of various options. The configuration
register 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 microcontroller unit (MCU), it is recommended that
this register be written immediately after reset. The configuration register is located at $001F and may be
read at anytime.
NOTE
On a FLASH device, the options are one-time writeable by the user after
each reset. The registers are not in the FLASH memory but are special
registers containing one-time writeable latches after each reset. Upon a
reset, the configuration register defaults to predetermined settings as
shown in
Figure 5-1 .
If the LVI module and the LVI reset signal are enabled, a reset occurs when
V
DD
falls to a voltage, V
LVRx
, and remains at or below that level for at least
nine consecutive central processor unit (CPU) cycles. Once an LVI reset
occurs, the MCU remains in reset until V
DD
rises to a voltage, V
LVRX
.