MEC1404 Datasheet, PDF (114/572 Pages) Microchip Technology – Keyboard and Embedded Controller Products for Notebook PC

MEC140X/1X
previous sample phase. During the turn-around phase, the controller must tri-state the SERIRQ. The device drives the
SERIRQ line low at the appropriate sample point if its associated IRQ/Data line is low, regardless of which device initi-
ated 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, then the
sample phase is {(6 x 3) - 1 = 17} the seventeenth clock after the rising edge of the Start Pulse.
TABLE 4-9: SERIRQ SAMPLING PERIODS
SERIRQ Period
Signal Sampled
# of Clocks Past Start
1
Not Used
2
2
IRQ1
5
3
IRQ2
8
4
IRQ3
11
5
IRQ4
14
6
IRQ5
17
7
IRQ6
20
8
IRQ7
23
9
IRQ8
26
10
IRQ9
29
11
IRQ10
32
12
IRQ11
35
13
IRQ12
38
14
IRQ13
41
15
IRQ14
44
16
IRQ15
47
The SIRQ data frame will now support IRQ2 from a logical device; previously SERIRQ Period 3 was reserved for use
by the System Management Interrupt (LSMI#). When using Period 3 for IRQ2, the user should mask off the SMI via the
ESMI Mask Register. Likewise, when using Period 3 for LSMI#, the user should not configure any logical devices as
using IRQ2.
SERIRQ Period 14 is used to transfer IRQ13. Each Logical devices will have IRQ13 as a choice for their primary inter-
rupt.
STOP CYCLE CONTROL
Once all IRQ/Data Frames have completed, the host controller will terminate SERIRQ activity by initiating a Stop Frame.
Only the host controller can initiate the Stop Frame. A Stop Frame is indicated when the SERIRQ is low for two or three
clocks. If the Stop Frame’s low time is two clocks, then the next SERIRQ cycle’s sampled mode is the Quiet mode; and
any SERIRQ device may initiate a Start Frame in the second clock or more after the rising edge of the Stop Frame’s
pulse. If the Stop Frame’s low time is three clocks, then the next SERIRQ cycle’s sampled mode is the continuous mode,
and only the host controller may initiate a Start Frame in the second clock or more after the rising edge of the Stop
Frame’s pulse.
DS00001956D-page 114
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