Advanced Notebook I/O for ISA or LPC Designs
Datasheet
Rev. 0.5 (03-24-05)
Page 26
SMSC SIO10N268
DATASHEET
Note 4.2
The LPCPD# pin may be tied high. The LPC interface will function properly if the PCI_RESET# signal
follows the protocol defined for the LRESET# signal in the “Low Pin Count Interface Specification”.
Note 4.3
If the 32kHz input clock is not used the CLKI32 pin must be grounded. There is a bit in the configuration
register at CR1E that determines whether the 32KHz clock input is used as the clock source for the WDT
and the LED’s. Set this bit to ‘1’ if the clock is not connected.
Note 4.4
The FDD output pins multiplexed in the PARALLEL PORT INTERFACE are OD drivers only and are not
affected by the FDD Output Driver Controls (see subsection CR05 in the Configuration section).
Note 4.5
Active (push-pull) output drivers are required on these pins in the enhanced parallel port modes.
Note 4.6
The nRTS1/SYSOPT pin requires an external pulldown resistor to put the base I/O address for
configuration at 0x02E.
An external pullup resistor is required to move the base I/O address for
configuration to 0x04E.
Note 4.7
The GP21/IRTX2/WDT pin is tristate when VCC=0. The pin comes up as an output and low following a
VCC POR and Hard Reset if configured for IRTX2 function. The GP21/IRTX2/WDT pin will remain low
following a power-up (VCC POR) if configured for IRTX2 until serial port 2 is enabled by setting the
UART2 Power bit to ‘1’. Once the power has been applied the pin will reflect the state of the IR transmit
output of the IRCC block. If this pin is configured for GPIO function, the pin will reflect the state of the
GPIO on a VCC POR.
Note 4.8
The GP53/TXD2/IRTX pin defaults to tristate when the part is under VTR power (VCC=0). The pin
comes up tristate following a VTR POR, VCC POR, and Hard Reset.
If the pin is configured for
alternate functions TXD2 or IRTX the GP53/TXD2/IRTX pin will remain tristate following a power-up
(VCC POR) until the UART2 Power bit is set to ‘1’. Once the power has been applied to the UART, the
pin will reflect the current state of the output transmit buffer. If this pin is configured for GPIO function,
the pin will reflect the state of the GPIO on a VCC POR.
Note 4.9
VTR can be connected to VCC if no wakeup functionality is required.
Note 4.10
VCC must not be greater than 0.5V above VTR.
Note 4.11
The nLED1 pin is powered by VCC and can only be controlled when the part is under VCC power.
Note 4.12
The nLED2 pin is powered by VTR so that the LED can be controlled when the part is under VTR power.
Note 4.13
The LPC_ISA pin may be connected directly to VCC to select ISA Mode (a pull-up is not recommended,
but one less than 1k ohms can be used). It can either be left unconnected or connected to ground to
select LPC Mode. The pin has a 30uA internal pulldown.
Note 4.14
These GPIO pins only have push-pull buffers. They cannot be configured for open drain outputs.
Note 4.15
MEMEN is a strapping option to enable/disable memory decoding on the LPC interface for the X-Bus.
When MEMEN is asserted (high), the LPC interface will decode memory or FWH addresses for the X-
Bus. When MEMEN is deasserted (low), the LPC interface will not decode memory or FWH addresses
Note 4.16
FWHSEL is a strapping option to determine the type of memory cycle decoded when the MEMEN
strapping option is asserted.
Assuming X-Bus memory cycles are enabled (MEMEN = 1), when
FWHSEL is asserted (high) FWH memory cycles are decoded for the X-Bus. When FWHSEL is
deasserted (low), LPC memory cycles are decoded for the X-Bus. If MEMEN=0, FWHSEL is has no
effect (i.e., Don’t Care).
Note 4.17
These pins have input buffers into the wakeup logic that are powered by VTR.