MEC1322 Datasheet, PDF (80/456 Pages) Microchip Technology – Keyboard and Embedded Controller for Notebook PC

MEC1322
5.8.1.3 LPC Clock Run
USING CLKRUN#
CLKRUN# is used to indicate the status of LCLK as well as to request that a stopped clock be started. See FIGURE
5-2: CLKRUN# System Implementation Example on page 81, an example of a typical system implementation using
CLKRUN#.
LCLK Run Support can be enabled and disabled via SIRQ_MODE as shown in Table 5-9, "LPC Controller CLKRUN#
Function". When the SIRQ_MODE is ‘0,’ Serial IRQs are disabled, the CLKRUN# pin is disabled, and the affects of Inter-
rupt requests on CLKRUN# are ignored. When the SIRQ_MODE is ‘1,’ Serial IRQs are enabled, the CLKRUN# pin is
enabled, and the CLKRUN# support related to Interrupts requests as described in the section below is enabled.
The CLKRUN# pin is an open drain output and input. Refer to the PCI Mobile Design Guide Rev 1.0 for a description
of the CLKRUN# function. If CLKRUN# is sampled “high”, LCLK is stopped or stopping. If CLKRUN# is sampled “low”,
LCLK is starting or started (running).
CLKRUN# Support for Serial IRQ Cycle
If a logical device asserts or de-asserts an interrupt and CLKRUN# is sampled “high”, the LPC Controller can request
the restoration of the clock by asserting the CLKRUN# signal asynchronously (Table 5-9). The LPC Controller holds
CLKRUN# low until it detects two rising edges of the clock. After the second clock edge, the controller must disable the
open drain driver (Figure 5-3).
The LPC Controller must not assert CLKRUN# if it is already driven low by the central resource; i.e., the PCI CLOCK
GENERATOR in Figure 5-2. The controller does not assert CLKRUN# under any conditions if the Serial IRQs are dis-
abled.
The LPC Controller must not assert CLKRUN# unless the line has been de-asserted for two successive clocks; i.e.,
before the clock was stopped (Figure 5-3).
The LPC Controller does not assert CLKRUN# if it is already driven low by the central resource; i.e., the PCI CLOCK
GENERATOR. The LPC Controller also does not assert CLKRUN# unless the signal has been de-asserted for two
successive clocks; i.e., before the clock was stopped.
TABLE 5-9: LPC CONTROLLER CLKRUN# FUNCTION
SIRQ_MODE
(Note 5-5)
Internal Interrupt
Or DMA Request
CLKRUN#
Action
0
1
Note 5-5
X
X
None
NO CHANGE
X
None
CHANGE (Note 5-6)
0
None
1
Assert CLKRUN#
SIRQ_MODE is defined in Section 5.8.4.1, "Enabling SERIRQ Function," on page 84.
Note 5-6
“Change” means either-edge change on any or all parallel IRQs routed to the Serial IRQ block. The
“change” detection logic must run asynchronously to LCLK and regardless of the Serial IRQ mode;
i.e., “continuous” or “quiet”.
DS00001719D-page 80
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