W83627EG Nuvoton Technology Corporation of America, W83627EG Datasheet - Page 197

• Manufacturer Part Number: W83627EG
• Description: IC I/O CONTROLLER 128-QFP
• Manufacturer: Nuvoton Technology Corporation of America

Specifications of W83627EG

• Applications: PC's, PDA's
• Interface: LPC
• Voltage - Supply: 3.3V
• Package / Case: 128-XFQFN
• Mounting Type: Surface Mount
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

W83627EHF/EF, W83627EHG/EG
13. SERIALIZED IRQ
The W83627EHF/EHG/EF/EG 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.
13.1 Start Frame
There are two modes of operation for the SERIRQ Start Frame: Quiet mode and Continuous mode.
In the Quiet mode, the W83627EHF/EHG/EF/EG drives the SERIRQ signal active low for one clock,
and then tri-states it. This brings all the state machines of the W83627EHF/EHG/EF/EG 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.
Start Frame Timing with source sampled a low pulse on IRQ1.
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