Compaq EV68A specifications Effect on IPRs After Transition Through Sleep Mode

Energy Star Certification and Sleep Mode Flow

After the PLL has finished ramping down, the reset state machine enters the WAIT_INTERRUPT state. Note the effects of the entry into that state on the IPRs listed in Table 7–6.

Table 7–6 Effect on IPRs After Transition Through Sleep Mode

IPR	Effects After Transition Through Sleep Mode
PAL_BASE	Maintained (not reset)
I_CTL	Bit value = 3 (both Icaches are enabled)
PCTX[FPE]	Set
WRITE_MANY	Cleared (That is, the WRITE_MANY chain is initialized and the Bcache is
	turned off.)

Note that Interrupt enables are maintained during sleep mode, enabling the 21264/ EV68A to wake up. The 21264/EV68A waits for either an unmasked clock interrupt or an unmasked device interrupt from the system.

When an enabled interrupt occurs, the PLL ramps back to full frequency. Subsequent to that, the 21264/EV68A performs a built-in self-initialization (BiSI), a shortened built-in self-test, which initializes the internal arrayed structures. The SROM is not reloaded.

Instead, the 21264/EV68A begins fetching code from the system at address PAL_BASE + 0x780.

Figure 7–3shows the sleep mode sequence of operations. In Figure 7–3,note the fol- lowing constraint and informational symbols:

Constraints:

A Min = 1 FrameClk_x cycle

Informational symbols:

aApproximately 525 GCLK cycles for external framing clock to be sampled and captured

bNext FrameClk_x rising edge

c1 FrameClk_x cycle

d3 FrameClk_x cycles

eApproximately 264 GCLK cycles to prevent first command from appearing too early

fApproximately 8192 GCLK cycles for BiSI

g16 GCLK cycles

7–10Initialization and Configuration 21264/EV68A Hardware Reference Manual