PCI950 Datasheet, PDF (3/11 Pages) Texas Instruments – IRQSER DESERIALIZER

PCI950
IRQSER DESERIALIZER
SCPS015A – JULY 1997 – REVISED JANUARY 1998
functional description
The PCI950 accepts the serialized IRQ stream from the PC Card controller for conversion to discrete ISA and
PCI interrupts. The serialized IRQ protocol is defined in the document Serialized IRQ Protocol for PCI Systems,
revision 6.0. This protocol uses a serial packet consisting of one start frame, several IRQ/data frames, and one
stop frame.
Start frame: There are two modes of operation for the IRQSER start frame – quiet mode and continuous mode.
During continuous mode the PCI950 initiates the start frame. A low level on the POLLMODE input pin selects
the quiet mode and a high level selects continuous mode for the PCI950. The total low-pulse width on a start
frame is eight clocks. After reset the PCI950 defaults to continuous mode.
IRQ/data frame: The PCI950 is designed to decode a fixed length of 21 IRQ/data frames that are sampled in
the following sequence: IRQ0, IRQ1, SMI, IRQ3 through IRQ15, IOCHK, INTA, INTB, INTC, and INTD.
Stop frame: After the completion of a start frame and 21 IRQ data frames, the PCI950 generates a stop frame.
The pulse width of the stop pulse is determined by the status of the POLLMODE input pin sampled during the
start frame.
Start Frame
(see Notes 2 and 3)
RT
IRQ0
S RT
IRQ1
SRT
IRQ2
SR T
IRQ3
IRQ4
S R T S RT
–––
PCLK
IRQSER
DRIVE
2 PCI950
Legend:
None
R = Recovery
S = Sample
T = Turnaround
NOTES: 2. Start frame is eight clocks in duration.
3. Slave or host initiated: POLLMODE is level dependent.
IRQ3
Figure 1. IRQSER Start-Frame Timing
None
IRQ15
S RT
IOCHK
SRT
INTA
SR T
INTB
SRT
INTC
S RT
INTD
S RT
Stop Frame
I
(see Notes 4 and 5) (see Note 6)
I
RT
PCLK
IRQSER
DRIVE IRQ15
Legend:
None
R = Recovery
S = Sample
T = Turnaround
I = Idle
PCI950
NOTES: 4. The PCI950 stop pulse is two or three clocks in duration.
5. There may be none, one, or more idle states during the stop frame.
6. When the PCI950 is in continuous mode, there are 17 idle states between the stop frame and the start frame.
Figure 2. IRQSER Stop-Frame Timing
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