FDC37M607 datasheet(110/182 Pages) SMSC

110 / 182 page

110

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.

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 FDC37M60x)

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.

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

defaulted

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.

IRQSER Data Frame

Once a Start Frame has been initiated, the

FDC37M60x will watch for the rising edge of the

Start Pulse and start counting IRQ/Data Frames

from there.

Each IRQ/Data Frame is three

clocks: Sample phase, Recovery phase, and

Turn-around phase. During the Sample phase

the FDC37M60x must drive the IRQSER (SIRQ

pin) low, if and only if, its last detected IRQ/Data

value was low. If its detected IRQ/Data value is

high, IRQSER must be left tri-stated. During the

Recovery phase the FDC37M60x must drive the

SERIRQ high, if and only if, it had driven the

IRQSER low during the previous Sample Phase.

During the Turn-around Phase the FDC37M60x

must tri-state the SERIRQ. The FDC37M60x will

drive the IRQSER line low at the appropriate

sample point if its associated IRQ/Data line is

low, regardless of which device initiated the

Start Frame.

The Sample Phase for each IRQ/Data follows

the low to high transition of the Start Frame

pulse by a number of clocks equal to the

IRQ/Data Frame times three, minus one. (e.g.

The IRQ5 Sample clock is the sixth IRQ/Data

Frame, (6 x 3) - 1 = 17th clock after the rising

edge of the Start Pulse.)

FDC37M607 Datasheet(PDF) 110 Page - SMSC Corporation

FDC37M607 Datasheet(HTML) 110 Page - SMSC Corporation

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