SCH3112I-NE SMSC [SMSC Corporation], SCH3112I-NE Datasheet - Page 194

• Manufacturer Part Number: SCH3112I-NE
• Description: LPC IO with 8042 KBC, Reset Generation, HWM and Multiple Serial Ports
• Manufacturer: SMSC [SMSC Corporation]

Rev 0.2 (09-28-04)
20.5.3
SPEKEY SCAN
Bit[3]
X
X
CODE
Bit[2]
Note: In multi-byte scan codes the most significant byte (MSB) will be received first.
0
1
Notes:
■
■
Once a valid make code is detected the wake on specific key logic will generate a KB_PB_STS wake
event (see
signal when in SX power state or below. PME_STS1 for description of the PME support for this PME
event
System for Decoding Scan Code Break Bytes Received from the
To accommodate different keyboards, there are three options for determining when the wake on
specific key logic deasserts the KB_PB_STS wake event (See in
in PME_STS1 and PME_STS1. Deassertion of the KB_PB_STS internally does not deasset the PME
status bit.
The Keyboard Power Button Release bits (Bits [4:5]) in PME_STS1 register may select these
KB_PB_STS options. See
each option is shown below.
Keyboard
X’ represents a don’t care.
By default, any time the KCLK signal is high or low for a nominal 125usec during the transmission
of a byte the scan code decode cycle will be reset and the next byte received will be treated as
the first byte received in the scan code byte sequence.
BYTES IN MAKE
NUMBER OF
Table 20.4 Decoding Keyboard Scan Code for Make Code
Figure
CODE
1 byte
2 byte
20.1). This wake event may be used to generate the assertion of the nIO_PME
The wake on specific key logic will compare each valid data byte
received with the Keyboard Scan Code – Make Byte 1 located in the
Runtime Register block at offset 5Fh. If the data byte received matches
the value stored in the register, a wake on specific key status event will
be generated. This wake event may be used to generate the assertion
of the nIO_PME signal. PME_STS1.
Note:
The wake on specific key logic compares each valid data byte received
with the value programmed in the Keyboard Scan Code – Make Byte 1
located in the Runtime Register block at offset 5Fh. If the data byte
received matches the value stored in the register, the hardware
compares the next byte received with the value programmed in the
Keyboard Scan Code – Make Byte 2 located in the Runtime Register
block at offset 60h. If the consecutive bytes received match the
programmed values, a wake on specific key status event is generated.
If the values do not match, if a parity error occurs, or if a timeout occurs,
the state machine is reset and the process is repeated. If a specific key
status event is generated then it may be used to generate the assertion
of the nIO_PME signal. PME_STS1
Note:
Chapter 26, "Runtime Register," on page
DATASHEET
LPC IO with 8042 KBC, Reset Generation, HWM and Multiple Serial Ports
If the value programmed in Keyboard Scan Code – Make Byte
1 is 00h it is treated as a don’t care and any valid scan code
being compared to this byte will be a match.
If the value programmed in Keyboard Scan Code – Make Byte
1 or Keyboard Scan Code -Make Byte2 is 00h it is treated as a
don’t care and any valid scan code being compared to this byte
will be a match.
178
DESCRIPTION
Figure
293. A detailed description of
20.1) going to the sticky bits
SMSC SCH311X
Datasheet