HD64F2149 Datasheet, PDF (649/1035 Pages) Renesas Technology Corp – Hitachi 16-Bit Single-Chip Microcomputer

18B.3.6 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 18B.7.
CLK
CLKRUN
1
2
3
4
5
6
Pull-up enable
Drive by the slave processor
Drive by the host processor
Figure 18B.7 Clock Start or Speed-Up
Cases other than SERIRQ in quiet mode when clock restart is required must be handled with a
different protocol, using the PME signal, etc.
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