NCT6627UD Nuvoton Technology Corporation of America, NCT6627UD Datasheet - Page 160

• Manufacturer Part Number: NCT6627UD
• Manufacturer: Nuvoton Technology Corporation of America

Specifications of NCT6627UD

• Lead Free Status / Rohs Status: Supplier Unconfirmed

14. SERIALIZED IRQ
The W83627UHG supports a serialized IRQ scheme. This allows a signal line to be used to report the parallel
interrupt requests. Since more than one device may need to share the signal serial SERIRQ signal, an open drain
signal scheme is employed. The clock source is the PCI clock. The serialized interrupt is transferred on the
SERIRQ signal, one cycle consisting of three frames types: the Start Frame, the IRQ/Data Frame, and the Stop
Frame.
There are two modes of operation for the SERIRQ Start Frame: the Quiet mode and the Continuous mode.
In the Quiet mode, the W83627UHG drives the SERIRQ signal active low for one clock, and then tri-states it. This
brings all the state machines of the W83627UHG from idle to active states. The host controller (the South Bridge)
then takes over driving SERIRQ signal low in the next clock and continues driving the SERIRQ low for
programmable 3 to 7 clock periods. This makes the total number of clocks low 4 to 8 clock periods. After these
clocks, the host controller drives the SERIRQ high for one clock and then tri-states it.
In the Continuous mode, the START Frame can only be initiated by the host controller to update the information
of the IRQ/Data Frame. The host controller drives the SERIRQ signal low for 4 to 8 clock periods. Upon a reset,
the SERIRQ signal is defaulted to the Continuous mode for the host controller to initiate the first Start Frame.
Please see the diagram below for more details.
PCICLK
SER IRQ
Drive Source
H=Host Control
Note:
2. The Start Frame pulse can be 4-8 clocks wide.
3. The first clock of Start Frame is driven low by the W83627UHG because IRQ1 of the W83627UHG needs an
14.1 Start Frame
IRQ1
SL
Figure 14-1 Start Frame Timing with Source Sampled A Low Pulse on IRQ1
or
H
2
START
Host Controller
START FRAME
H
SL=Slave Control
1
R
T
IRQ0 FRAME
S
None
R
R=Recovery
T
-151-
IRQ1 FRAME
S
W83627UHG/NCT6627UD
IRQ1
R
Publication Release Date: October 26, 2010
T
T=Turn-around
SMI# FRAME
S
None
R
T
Revision 1.7
S=Sample