SMH4042
CompactPCI Applications Aid
• The long pins engage.
• Power is supplied to the SMH4042, the LED and the BD_SEL” pull-up resistor.
• V(I/O) is either the early 5V or the early 3V, dependent upon the interface operating levels.
• The LED is illuminated by LOCAL_PCI_RST# going low.
• The medium length pins contact.
• The ENUM# signal should not be active at this point.
• The board is fully inserted and the injector switch is closed.
• ENUM# is driven low.
• BD_SEL# makes contact (optional: the pull-up on the board indicates to the host the presence of a board.)
• The host responds to the ENUM# signal and drives BD_SEL# low.
• This provides the last gating item to the SMH4042 before it will begin the power-on sequence.
Switching + and -12Volts
In some applications there may be a need to switch + or -12Volts to the backend circuits. Using the SMH4042
DRVREN# output these voltages can be controlled as shown in the Figure 9 below:
V(I/O)
Board
Platform
PRESENT
BD_SEL#
BD_SEL1#
LOCAL_PCI_RESET#
LOCAL_PCI_RESET#
Power ON
RESET
3.9KΩ
eP
SMH4042
RLIM
V(I/O)
10KΩ
BD_SEL2#
PCI_RST#
PCI_RST#
eP
Open Collector
eP
ENUM#
Board Status
EIM=0 INS EXT
2037 ILL30.0
Figure 9.Full HotSwap board/host interface
2037-07 9/23/99
20
SUMMIT [ SUMMIT MICROELECTRONICS, INC. ]
