MEC1404 Datasheet, PDF (418/572 Pages) Microchip Technology – Keyboard and Embedded Controller Products for Notebook PC

MEC140X/1X
Note: A weak pull-up resistor is recommended on the data line (100K
The maximum speed at which the BC-Link Master Interface can operate reliably depends on the drive strength of the
BC-Link BCM_CLK and BCM_DAT pins, as well as the nature of the connection to the Companion device (over ribbon
cable or on a PC board). The following table shows the recommended maximum speeds over a PC board as well as a
12 inch ribbon cable for selected drive strengths. The frequency is set with the BC-Link Clock Select Register.
TABLE 31-2: BC-LINK MASTER PIN DRIVE STRENGTH VS. FREQUENCY
Pin Drive
Strength
16mA
Max Freq
on PC Board
24Mhz
Min Value in
BC-Link Clock
Select Register
1
Max Freq
over Ribbon cable
Min Value in BC-
Link Clock Select
Register
16Mhz
2
31.6 Host Interface
The registers defined for the BC-Link Master Interface are accessible by the various hosts as indicated in Section 31.11,
"EC-Only Registers".
31.7 Power, Clocks and Reset
31.7.1 POWER DOMAINS
VTR
Name
31.7.2 CLOCK INPUTS
Description
The logic and registers implemented in this block are powered by this
power well.
Name
48 MHz Ring Oscillator
31.7.3 RESETS
Description
This is the clock source for Keyboard Scan Interface logic.
nSYSRST
Name
Description
This signal resets all the registers and logic in this block to their default
state.
DS00001956D-page 418
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