Table 5-17 HALT Mode Switching Characteristics
PARAMETER |
MIN |
TYP |
MAX |
UNIT |
td(IDLE-XCOL) |
Delay time, IDLE instruction executed to XCLKOUT low |
32tc(SCO) |
|
45tc(SCO) |
cycles |
tp |
PLL lock-up time |
|
|
131072tc(OSCCLK) |
cycles |
td(WAKE-HALT) |
Delay time, PLL lock to program execution resume
- Wake up from flash
- Flash module in sleep state
|
|
|
1125tc(SCO) |
cycles |
|
|
|
35tc(SCO) |
cycles |
A. IDLE instruction is executed to put the device into HALT mode.
B. The PLL block responds to the HALT signal. SYSCLKOUT is held for approximately 32 cycles (if CLKINDIV = 0) or 64 cycles (if CLKINDIV = 1) before the oscillator is turned off and the CLKIN to the core is stopped. This delay enables the CPU pipe and any other pending operations to flush properly.
C. Clocks to the peripherals are turned off and the PLL is shut down. If a quartz crystal or ceramic resonator is used as the clock source, the internal oscillator is shut down as well. The device is now in HALT mode and consumes absolute minimum power.
D. When the GPIOn pin (used to bring the device out of HALT) is driven low, the oscillator is turned on and the oscillator wake-up sequence is initiated. The GPIO pin should be driven high only after the oscillator has stabilized. This enables the provision of a clean clock signal during the PLL lock sequence. Since the falling edge of the GPIO pin asynchronously begins the wakeup process, care should be taken to maintain a low noise environment prior to entering and during HALT mode.
E. Once the oscillator has stabilized, the PLL lock sequence is initiated, which takes 131,072 OSCCLK (X1/X2 or X1 or XCLKIN) cycles. Note that these 131,072 clock cycles are applicable even when the PLL is disabled (that is, code execution will be delayed by this duration even when the PLL is disabled).
F. Clocks to the core and peripherals are enabled. The HALT mode is now exited. The device will respond to the interrupt (if enabled), after a latency.
G. Normal operation resumes.
H. The wake-up signal fed to a GPIO pin to wake up the device must meet the minimum pulse width requirement. Furthermore, this signal must be free of glitches. If a noisy signal is fed to a GPIO pin, the wake-up behavior of the device will not be deterministic.
I. From the time the IDLE instruction is executed to place the device into low-power mode (LPM), wakeup should not be initiated until at least 4 OSCCLK cycles have elapsed.
Figure 5-11 HALT Wake-Up Using GPIOn