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ulp: document the need to wait for RTC to be ready for wakeup

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Ivan Grokhotkov
2017-12-07 17:11:24 +08:00
parent b6a6973b44
commit ca751648fa
4 changed files with 25 additions and 5 deletions
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12
docs/api-guides/ulp_instruction_set.rst
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@@ -573,11 +573,17 @@ Similar considerations apply to ``LD`` and ``ST`` instructions. Consider the fol
- If the SoC is not in deep sleep mode, and ULP interrupt bit (RTC_CNTL_ULP_CP_INT_ENA) is set in RTC_CNTL_INT_ENA_REG register, RTC interrupt will be triggered.
Note that before using WAKE instruction, ULP program may needs to wait until RTC controller is ready to wake up the main CPU. This is indicated using RTC_CNTL_RDY_FOR_WAKEUP bit of RTC_CNTL_LOW_POWER_ST_REG register. If WAKE instruction is executed while RTC_CNTL_RDY_FOR_WAKEUP is zero, it has no effect (wake up does not occur).
**Examples**::
1: WAKE // Trigger wake up
REG_WR 0x006, 24, 24, 0 // Stop ULP timer (clear RTC_CNTL_ULP_CP_SLP_TIMER_EN)
HALT // Stop the ULP program
1: is_rdy_for_wakeup: // Read RTC_CNTL_RDY_FOR_WAKEUP bit
READ_RTC_FIELD(RTC_CNTL_LOW_POWER_ST_REG, RTC_CNTL_RDY_FOR_WAKEUP)
AND r0, r0, 1
JUMP is_rdy_for_wakeup, eq // Retry until the bit is set
WAKE // Trigger wake up
REG_WR 0x006, 24, 24, 0 // Stop ULP timer (clear RTC_CNTL_ULP_CP_SLP_TIMER_EN)
HALT // Stop the ULP program
// After these instructions, SoC will wake up,
// and ULP will not run again until started by the main program.