Datasheet

Oscillator Module (OSC)
Input/Output (I/O) Registers
MC68HC908QY4•MC68HC908QT4•MC68HC908QY2•MC68HC908QT2•MC68HC908QY1•MC68HC908QT1
MOTOROLA Oscillator Module (OSC) 111
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8.9 Input/Output (I/O) Registers
The oscillator module contains these two registers:
1. Oscillator status register (OSCSTAT)
2. Oscillator trim register (OSCTRIM)
8.9.1 Oscillator Status Register
The oscillator status register (OSCSTAT) contains the bits for switching
from internal to external clock sources
ECGON — External Clock Generator On Bit
This read/write bit enables external clock generator, so that the
switching process can be initiated. This bit is forced low during reset.
This bit is ignored in monitor mode with the internal oscillator
bypassed, PTM or CTM mode.
1 = External clock generator enabled
0 = External clock generator disabled
ECGST — External Clock Status Bit
This read-only bit indicates whether or not an external clock source is
engaged to drive the system clock.
1 = An external clock source engaged
0 = An external clock source disengaged
Address: $0036
Bit 7654321Bit 0
Read:
RRRRRRECGON
ECGST
Write:
Reset: 0 0 0
00
000
R=Reserved
Figure 8-3. Oscillator Status Register (OSCSTAT)