MEC1404 Datasheet, PDF (71/572 Pages) Microchip Technology – Keyboard and Embedded Controller Products for Notebook PC

MEC140X/1X
TABLE 3-5: SOURCE CLOCK DEFINITIONS
Clock Name
SUSCLK
32.768 kHz Crystal
Oscillator
48 MHz Ring
Oscillator
Frequency
32.768 kHz
32.768 kHz
48 MHz
Description
Source
32.768 kHz Suspend Well Clock
Source is a single-ended input that
is an accurate 32.768 kHz clock.
(Note 3-5)
Pin Interface (XTAL2)
A 32.768 kHz parallel resonant crys-
tal connected between the XTAL1
and XTAL2 pins.
Pin Interface (XTAL1 and XTAL2)
The 48 MHz Ring Oscillator is a
high-accuracy, low power, low start-
up latency 48 MHz Ring Oscillator.
Internal Oscillator powered by VTR.
May be stopped by Chip Power
Management Features.
32kHz_INT_OSC
32.768 kHz
(Note 3-6)
32.768 kHz low power, lower accu-
racy Internal Oscillator powered by
VBAT supply.
Note:
This clock may be used
when the external 32
kHz clock is unavailable,
and will allow the 48
MHz clock to reach fre-
quency lock.
Internal Oscillator
Note:
This clock source is
enabled via the Clock
Enable Register on page
444.
Note 3-5
Note 3-6
Note 3-7
The chipset will not produce a valid 32 kHz clock until about 5 ms (PCH) or 110 ms (ICH) after the
deassertion of RSMRST#. See chipset specification for the actual timing.
The 48 MHz Ring Oscillator will reach frequency lock if either the external 32kHz clock source or the
32 kHz Internal Oscillator is used, as selected via the 48MHz Oscillator Reference Select bit in the
Clock Enable Register on page 444. The external 32k Hz clock source provides a stable timebase
for the 48 MHz Ring Oscillator as well as the clock source for the 32 kHz Clock Domain. After VBAT
POR there is a 500ms max time for the 48 MHz Ring Oscillator to become accurate. See Section
43.2, "Clocking AC Timing Characteristics," on page 506.
Without the external clock, the 48MHz clock will vary up to +/-4% which may affect the timing
parameters of certain blocks. In particular it may not be accurate enough to ensure that the UART
will work, depending on the accuracy of the clock of the external device.
3.5.2 DERIVED CLOCKS
This table defines the clocks derived from the raw clock sources.
TABLE 3-6: DERIVED CLOCK DEFINITIONS
Clock Name
EC_PROC_CLK
24MHz_Clk
16MHz_Clk
2MHz_Clk
Frequency
Programma-
ble
24 MHz
16 MHz
2 MHz
Description
Derived clock for Embedded Con-
troller/Processor
Derived clock for UART
Derived clock for SMBus Controller
Derived clock for PS/2 Controller
Source
48 MHz Ring Oscillator
48 MHz Ring Oscillator
48 MHz Ring Oscillator
48 MHz Ring Oscillator
 2015 - 2016 Microchip Technology Inc.
DS00001956D-page 71