h8s-2649 Renesas Electronics Corporation., h8s-2649 Datasheet - Page 622

• Manufacturer Part Number: h8s-2649
• Description: Renesas 16-bit Single-chip Microcomputer H8s Family/h8s/2600 Series
• Manufacturer: Renesas Electronics Corporation.

Section 21 Power-Down Modes
21.5
When the STBY pin is driven low, a transition is made to hardware standby mode from any mode.
In hardware standby mode, all functions enter the reset state and stop operation, resulting in a
significant reduction in power consumption. As long as the prescribed voltage is supplied, on-chip
RAM data is retained. The I/O ports are set to the high-impedance state.
In order to retain on-chip RAM data, the RAME bit in SYSCR should be cleared to 0 before
driving the STBY pin low.
Do not change the state of the mode pins (MD2 and MD0) while this LSI is in hardware standby
mode.
Hardware standby mode is canceled by signals at the STBY pin and the RES pin. When the STBY
pin is driven high while the RES pin is low, the reset state is entered and clock oscillation is
started. Ensure that the RES pin is held low until the clock oscillator stabilizes (at least 8 ms
(oscillation stabilization time) when using a crystal oscillator). When the RES pin is subsequently
driven high, a transition is made to the program execution state via the reset exception handling
state.
When the STBY pin is driven low after the RES pin has been driven low, a transition is made to
hardware standby mode. Hardware standby mode is canceled by driving the STBY pin high,
waiting for the oscillation stabilization time, then switching the RES pin from low to high.
Rev. 2.00 Dec. 05, 2005 Page 584 of 724
REJ09B0200-0200
Oscillator
RES
STBY
Hardware Standby Mode
Figure 21.4 Hardware Standby Mode Timing
Oscillation
stabilization
time
exception
handling
Reset