MEC1404 Datasheet, PDF (445/572 Pages) Microchip Technology – Keyboard and Embedded Controller Products for Notebook PC

MEC140X/1X
Address ^08h
Bits
Description
Type
Default
Reset
Event
2 INT_32K_OSC_EN
R/W
0b
VBAT_
0 = Internal 32kHz oscillator is disabled
(Note 35-3) POR
1 = Internal 32kHz oscillator is enabled. See Table 35-3, "32kHz
Clock Control" below for determining the source of the 32kHz clock.
1 EXT_32K_OSC_EN
0 = XOSEL control is disabled. All the External clock sources are
disabled.
1 = External clock selected by XOSEL is enabled.
R/W
0b
VBAT_
(Note 35-3) POR
0 XOSEL
R/W
0b
VBAT_
This bit controls whether a crystal or single ended clock source is
(Note 35-3) POR
used.
1= the 32.768 KHz Crystal Oscillator is driven by a single-ended
32.768 KHz clock source connected to the XTAL2 pin.
0= the 32.768 KHz Crystal Oscillator requires a 32.768 KHz parallel
resonant crystal connected between the XTAL1 and XTAL2 pins
(default).
Note 35-3
If the Boot ROM exception handler runs, the Boot ROM will reconfigure this register to 04h, enabling
the internal 32kHz clock source. This is done so the Boot ROM can issue a nSYSRST via a WDT
Event.
TABLE 35-3: 32KHZ CLOCK CONTROL
XOSEL
32KHz
Clock
Switcher
Control
EXT_32K_
OSC_EN
INT_32K_
OSC_EN
INT_32K
VTR
Power
Well
Emulation
32k Hz Clock Source
x
x
1
x
0
x
x
x
x
x
1
0
0
0
x
Disabled
1
0
x
Single-ended External Clock
1
x
x
External Crystal
0
1
0
Internal 32k Hz Clock - remains ON when VTR = 0V
0
1
1
Internal 32k Hz Clock - Turned OFF when VTR = 0V
1
1
0
Switched Clock Source:
- Primary Clock is Single-ended External Clock
when VTR is ON.
- When the primary clock is OFF or VTR is OFF the
internal 32k Hz clock is selected.
1
0
Note: If VTR = 0V the internal 32kHz clock is
ON.
1
1
1
Switched Clock Source:
- Primary Clock is Single-ended External Clock
when VTR is ON.
- When the primary clock is OFF or VTR is OFF the
internal 32k Hz clock is selected.
1
1
Note: If VTR = 0V the internal 32kHz clock is
OFF.
1
x
x
Single-ended External Clock
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DS00001956D-page 445