FDC37C672QFP SMSC Corporation, FDC37C672QFP Datasheet - Page 107

• Manufacturer Part Number: FDC37C672QFP
• Description: ENHANCED SUPER I/O CONTROLLER WITH FAST IR
• Manufacturer: SMSC Corporation

Enhanced Super I/O Controller with Fast IR
Datasheet
Note 1
Note 2
Note 3
14.1.2 IRQSER Cycle Control
SMSC FDC37C672
PCICLK
IRQSER
Driver
B.
Stop pulse is 2 clocks wide for Quiet mode, 3 clocks wide for Continuous mode.
There may be none, one or more Idle states during the Stop Frame.
The next IRQSER cycle’s Start Frame pulse may or may not start immediately after the turn-around clock
of the Stop Frame.
There are two modes of operation for the IRQSER Start Frame.
1.
2.
Stop Frame Timing with Host using 17 IRQSER sampling period
Quiet (Active) Mode: Any device may initiate a Start Frame by driving the IRQSER low for one clock,
while the IRQSER is Idle. After driving low for one clock the IRQSER must immediately be tri-stated
without at any time driving high. A Start Frame may not be initiated while the IRQSER is Active. The
IRQSER is Idle between Stop and Start Frames. The IRQSER is Active between Start and Stop
Frames. This mode of operation allows the IRQSER to be Idle when there are no IRQ/Data transitions
which should be most of the time.
Once a Start Frame has been initiated the Host Controller will take over driving the IRQSER low in the
next clock and will continue driving the IRQSER low for a programmable period of three to seven
clocks. This makes a total low pulse width of four to eight clocks. Finally, the Host Controller will
drive the IRQSER back high for one clock, then tri-state.
Any IRQSER Device (i.e., The FDC37C672) which detects any transition on an IRQ/Data line for
which it is responsible must initiate a Start Frame in order to update the Host Controller unless the
IRQSER is already in an IRQSER Cycle and the IRQ/Data transition can be delivered in that IRQSER
Cycle.
Continuous (Idle) Mode: Only the Host controller can initiate a Start Frame to update IRQ/Data line
information. All other IRQSER agents become passive and may not initiate a Start Frame. IRQSER
will be driven low for four to eight clocks by Host Controller. This mode has two functions. It can be
used to stop or idle the IRQSER or the Host Controller can operate IRQSER in a continuous mode by
initiating a Start Frame at the end of every Stop Frame.
An IRQSER mode transition can only occur during the Stop Frame. Upon reset, IRQSER bus is
defaulted to Continuous mode, therefore only the Host controller can initiate the first Start Frame.
Slaves must continuously sample the Stop Frames pulse width to determine the next IRQSER Cycle’s
mode.
S
FRAME
None
IRQ14
R
T
S
IRQ15
IRQ15
FRAME
H=Host Control
R=Recovery
R
DATASHEET
T
S
IOCHCK#
None
FRAME
I= Idle.
Page 107
R
T=Turn-around
S=Sample
T
I
2
STOP FRAME
Host Controller
STOP
H
1
R
T
NEXT CYCLE
START
Rev. 10-29-03
3