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Rev. 1.00, 05/04, page 407 of 544
15.4.6 Host Interface Clock Start Request (CLKRUN)
A request to restart the clock (LCLK) can be sent to the host processor by means of the CLKRUN
pin. With LPC data transfer and SERIRQ in continuous mode, a clock restart is never requested
since the transfer cycles are initiated by the host. With SERIRQ in quiet mode, when a host
interrupt request is generated the CLKRUN signal is driven and a clock (LCLK) restart request is
sent to the host. The timing for this operation is shown in figure 15.7.
CLK
CLKRUN
Pull-up enable
Drive by the host processor
Drive by the slave processor
1 2 3 4 5 6
Figure 15.7 Clock Start Request Timing
Cases other than SERIRQ in quiet mode when clock restart is required must be handled with a
different protocol, using the PME signal, etc.