LPC47M172_07 SMSC [SMSC Corporation], LPC47M172_07 Datasheet - Page 131

• Manufacturer Part Number: LPC47M172_07
• Description: Advanced I/O Controller with Motherboard GLUE Logic
• Manufacturer: SMSC [SMSC Corporation]

7.30
7.30.1 Hard Drive Front Panel LED (Red)
Notes:
SMSC LPC47M172
The nHD_LED requires external pull-up to VCC.
ISPU_400 is defined as: Input with Schmitt Trigger, 400 mV hysteresis, with 30uA internal pull-up.
The nHD_LED pin is a logical AND of the inputs nPRIMARY_HD, nSECONDARY_HD and nSCSI used to drive a
single color LED. The inputs are internally pulled to VCC. See table below for state definitions.
The nHD_LED pin is used at the system’s front panel header to drive the hard drive activity LED. Note that
external LEDs should be driven such that the voltage at the nHD_LED pin does not exceed 5V. The output is
open-drain and should be externally pulled to VCC through a resistor.
NPRIMARY_HD
event of a stalled fan. The internal count register does rollover, however, and continuously counts to
FFFFh as long as the fan is stalled.
In the event the counter reaches FFFFh, the PME status bit is set and the count value is latched into the
register. The second subsequent fan tach pulse resets the counter but does not latch the count value.
Every second fan tach pulse latches the fan count value into the fan tachometer register except for this
special case.
The fan stalled event can generate a PME if properly enabled. Note the fan stalled PME is not a wakeup
event, and it can indicate a fan stalled event if VCC is active.
Hard Drive and Power LED Logic
X
X
0
1
nSCSI
nHD_LED
nSECONDARY_HD
nPRIMARY_HD
NAME
NSECONDARY_HD
INPUTS
X
X
1
0
Table 7.20 - Hard Drive Front Panel Pins
Table 7.21 - nHD_LED Truth Table
ISPU_400
OD12
ISPU_400
ISPU_400
BUFFER
DATASHEET
Page 131
POWER
NSCSI
WELL
VCC
VCC
VCC
VCC
X
X
0
1
SCSI Drive Active Input
Hard Drive Front Panel LED
Open-Drain Output
IDE Secondary Drive Active
Input
IDE Primary Drive Active Input
Advanced I/O Controller with Motherboard GLUE Logic
DESCRIPTION
SMSC/Non-SMSC Register Sets (Rev. 01-11-07)
nHD_LED
OUTPUT
Hi-Z
0
0
0
LED Off
NOTES
LED On
LED On
LED On
Datasheet