Datasheet

Section 22 Power-Down Modes
Page 688 of 846 REJ09B0140-0900 Rev. 9.00
Sep 16, 2010
H8S/2215 Group
22.2 Medium-Speed Mode
When the SCK2 to SCK0 bits in SCKCR are set to 1, the operating mode changes to medium-
speed mode as soon as the current bus cycle ends. In medium-speed mode, the CPU operates on
the operating clock (φ/2, φ/4, φ/8, φ/16, or φ/32) specified by the SCK2 to SCK0 bits. The bus
masters other than the CPU (DTC or DMAC) also operate in medium-speed mode. On-chip
supporting modules other than the bus masters always operate on the high-speed clock (φ).
In medium-speed mode, a bus access is executed in the specified number of states with respect to
the bus master operating clock. For example, if φ/4 is selected as the operating clock, on-chip
memory is accessed in 4 states, and internal I/O registers in 8 states.
Medium-speed mode is cleared by clearing all of bits SCK2 to SCK0 to 0. A transition is made to
high-speed mode and medium-speed mode is cleared at the end of the current bus cycle.
If a SLEEP instruction is executed when the SSBY bit in SBYCR is cleared to 0, a transition is
made to sleep mode. When sleep mode is cleared by an interrupt, medium-speed mode is restored.
When the SLEEP instruction is executed with the SSBY bit = 1, operation shifts to the software
standby mode. When software standby mode is cleared by an external interrupt, medium-speed
mode is restored.
When the RES or MRES pin is set low and medium-speed mode is cancelled, operation shifts to
the reset state. The same applies in the case of a reset caused by overflow of the watchdog timer.
When the STBY pin is driven low, a transition is made to hardware standby mode.
Figure 22.2 shows the timing for transition to and clearance of medium-speed mode.