HD64F2638F20J Datasheet, PDF (986/1512 Pages) Renesas Technology Corp – Renesas 16-Bit Single-Chip Microcomputer H8S Family/H8S/2600 Series

Section 23A Power-Down Modes [HD64F2636F, HD64F2638F, HD6432636F,
HD6432638F, HD64F2630F, HD6432630F, HD64F2635F, HD6432635F, HD6432634F]
H8S/2639, H8S/2638, H8S/2636,
H8S/2630, H8S/2635 Group
23A.3 Medium-Speed Mode
In high-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) 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, and LSON bit in
LPWRCR 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, LPWRCR LSON bit = 0, and
TCSR (WDT1) PSS bit = 0, 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 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 23A-2 shows the timing for transition to and clearance of medium-speed mode.
Page 936 of 1458
REJ09B0103-0800 Rev. 8.00
May 28, 2010