MC68HC05L28 Datasheet, PDF (34/156 Pages) Motorola, Inc – Flexible general-purpose microcomputer

2.3.2 WAIT
2
The WAIT instruction places the MCU in a low power consumption mode, but the WAIT mode
consumes more power than the STOP mode. All CPU action is suspended, but the core timer,
16-bit timer and I²C remains active. An interrupt from the core timer, 16-bit timer or I²C (if enabled)
will cause the MCU to exit WAIT mode.
During WAIT mode, the I-bit in the CCR is cleared to enable interrupts. All other registers, memory
and input/output lines remain in their previous state. The core timer may be enabled to allow a
periodic exit from the WAIT mode (see Figure 2-6).
2.3.3 Data retention
The contents of the RAM are retained at supply voltages as low as 2.0Vdc. This is called the data
retention mode, in which data is maintained but the device is not guaranteed to operate.
For lowest power consumption in data retention mode the device should be put into STOP mode
before reducing the supply voltage, to ensure that all the clocks are stopped. If the device is not in
STOP mode then it is recommended that RESET be held low while the power supply is outside
the normal operating range, to ensure that processing is suspended in an orderly manner.
Recovery from data retention mode, after the power supply has been restored, is by pulling the
RESET line high.
To put the MCU into data retention mode:
• Set RESET pin to zero
• Reduce the voltage on VDD. RESET must remain low during data retention mode
To take the MCU out of data retention:
• Return VDD to normal operating level
• Return RESET to logical one.
MOTOROLA
2-12
MODES OF OPERATION AND PIN DESCRIPTIONS
TPG
MC68HC05L28