Datasheet

MC68HC908QY4•MC68HC908QT4•MC68HC908QY2•MC68HC908QT2•MC68HC908QY1•MC68HC908QT1

56 Configuration Register (CONFIG) MOTOROLA

Configuration Register (CONFIG)

NON-DISCLOSURE AGREEMENT REQUIRED

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 register is 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.

IRQPUD — IRQ Pin Pullup Control Bit

1 = Internal pullup is disconnected

0 = Internal pullup is connected between IRQ pin and V

IRQEN — IRQ Pin Function Selection Bit

1 = Interrupt request function active in pin

0 = Interrupt request function inactive in pin

OSCOPT1 and OSCOPT0 — Selection Bits for Oscillator Option

(0, 0) Internal oscillator

(0, 1) External oscillator

(1, 0) External RC oscillator

(1, 1) External XTAL oscillator

RSTEN — R

ST Pin Function Selection

1 = Reset function active in pin

0 = Reset function inactive in pin

NOTE: The RSTEN bit is cleared by a power-on reset (POR) only. Other resets

will leave this bit unaffected.

Address: $001E

Bit 7654321Bit 0

Read:

IRQPUD IRQEN R OSCOPT1 OSCOPT0 R R RSTEN

Write:

Reset:0000 000U

POR:000 0 0000

R = Reserved U = Unaffected

Figure 5-1 Configuration Register 2 (CONFIG2)