Renesas Hitachi H8S/2191, Hardware Manual

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Rev. 2.0, 11/00, page 56 of 1037
2.8.5 Power-Down State
The power-down state includes both modes in which the CPU stops operating and modes in
which the CPU does not stop. There are five modes in which the CPU stops operating: sleep
mode, standby mode, subsleep mode, and watch mode. There are also three other power-down
modes: medium-speed mode, module stop mode, and subactive mode. In medium-speed mode,
the CPU operates on a medium-speed clock. Module stop mode permits halting of the operation
of individual modules, other than the CPU. Subactive mode, subsleep mode, and watch mode
are power-down modes that use subclock input. For details, see section 4, Power-Down State.
(1) Sleep Mode
A transition to sleep mode is made if the SLEEP instruction is executed while the software
standby bit (SSBY) in the standby control register (SBYCR) and the LSON bit in the low-
power control register (LPWRCR) are both cleared to 0. In sleep mode, CPU operations stop
immediately after execution of the SLEEP instruction. The contents of CPU registers are
retained.
(2) Standby Mode
A transition to standby mode is made if the SLEEP instruction is executed while the SSBY
bit in SBYCR is set to 1 and the LSON bit in LPWRCR and the TMA3 bit in the TMA
(timer A) are both cleared to 0. In standby mode, the CPU and clock halt and all MCU
operations stop. As long as a specified voltage is supplied, the contents of CPU registers and
on-chip RAM are retained.