Medium-Speed Mode; Sleep Mode - Renesas H8S Series Hardware Manual

21.3

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 (ø/2, ø/4, ø/8, ø/16, or ø/32)
specified by the SCK2 to SCK0 bits. The bus masters other than the CPU (the DMAC and DTC) also operate in medium-
speed mode. On-chip supporting modules other than the bus masters always operate on the high-speed clock (ø).
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 ø/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.
If a SLEEP instruction is executed when the SSBY bit in SBYCR is set to 1, a transition is made to software standby
mode. When software standby mode is cleared by an external interrupt, medium-speed mode is restored.
When the RES pin is driven low, a transition is made to the reset state, and medium-speed mode is cleared. 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 21-1 shows the timing for transition to and clearance of medium-speed mode.
ø,
supporting module clock
Bus master clock
Internal address bus
Internal write signal
21.4

Sleep Mode

If a SLEEP instruction is executed when the SSBY bit in SBYCR is cleared to 0, the CPU enters sleep mode. In sleep
mode, CPU operation stops but the contents of the CPU's internal registers are retained. Other supporting modules do not
stop.
Sleep mode is cleared by a reset or any interrupt, and the CPU returns to the normal program execution state via the
exception handling state. Sleep mode is not cleared if interrupts are disabled, or if interrupts other than NMI are masked
by the CPU.
When the STBY pin is driven low, a transition is made to hardware standby mode.
Rev.6.00 Oct.28.2004 page 672 of 1016
REJ09B0138-0600H
SCKCR
Figure 21-1 Medium-Speed Mode Transition and Clearance Timing
Medium-speed mode
SCKCR