FDC37B78X SMSC Corporation, FDC37B78X Datasheet - Page 118

• Manufacturer Part Number: FDC37B78X
• Description: Enhanced Super I/O Controller with ACPI Support/ Real Time Clock and Consumer IR
• Manufacturer: SMSC Corporation

IRQSER Cycle Control
There are two modes of operation for the
IRQSER Start Frame.
1) Quiet (Active) Mode: Any device may initiate
a Start Frame by driving the IRQSER low for
one clock, while the IRQSER is Idle.
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.
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
PCICLK
IRQSER
Driver
B) Stop Frame Timing with Host using 17 IRQSER sampling period
1)
2)
3)
S
FRAME
None
IRQ14
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.
R
T
S
IRQ15
IRQ15
FRAME
R
H=Host Control
R=Recovery
T
After
The
S
IOCHCK#
None
FRAME
I= Idle.
118
R
Controller will drive the IRQSER back high for
one clock, then tri-state.
Any IRQSER Device (i.e., The FDC37B78x)
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.
2) Continuous (Idle) Mode: Only the Host
controller can initiate a Start Frame to update
IRQ/Data line information.
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,
T
I
T=Turn-around
S=Sample
2
STOP FRAME
Host Controller
STOP
H
1
R
T
All other IRQSER
NEXT CYCLE
START
3