W83877TF Datasheet, PDF (71/154 Pages) Winbond – I/O chip disk drive adapter

W83877TF
7.1 Start Frame
There are two modes of operation for the IRQSER Start frame: Quiet mode and Continuous mode.
In the Quiet mode, the peripheral drives the SERIRQ signal active low for one clock, and then tri-
states it. This brings all the states machines of the peripherals from idle to active states. the host
controller will then take over driving IRQSER signal low in the next clock and will continue driving the
IRQSER low for programmable 3 to 7 clock periods. This makes the total number of clocks low for 4
to 8 clock periods. After these clocks, the host controller will drive the IRQSER high for one clock and
then tri-stated.
In the Continuous mode, only the host controller initiates the START frame to update IRQ/Data line
information. The host controller drives the IRQSER signal low for 4 to 8 period clocks. Upon reset, the
IRQSER signal is defaulted to the Continuous mode for the host controller to initiate the first Start
frame.
7.2 IRQ/Data Frame
Once the start frame has been initiated, all the peripherals must start counting frames based on the
rising edge of the start pulse. Each IRQ/Data Frame is three clocks: Sample phase, Recovery phase,
and Turn-around phase.
During the Sample phase, the peripheral drives SERIRQ low if the corresponding IRQ should be
active. If the corresponding IRQ is inactive, then IRQSER must be left tri-stated. During the Recovery
phase, the peripheral device drives the IRQSER high. During the Turn-around phase, the peripheral
device left the IRQSER tri-stated.
The IRQ/Data Frame has a number of specific order, as shown in Table 7-1.
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Publication Release Date: March 1998
Version 0.61