Section 27 Power-Down Modes
Rev. 3.00 Jan 25, 2006 page 781 of 872
REJ09B0286-0300
27.3
Medium-Speed Mode
The CPU makes a transition to medium-speed mode as soon as the current bus cycle ends
according to the setting of the SCK2 to SCK0 bits in SBYCR. 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 RFU) also operate in medium-speed mode when the
DTSPEED bit in SBYCR is cleared to 0. Note however that the DTSPEED bit must be set to 1
when the RFU is used in medium-speed mode. On-chip peripheral modules other than the bus
masters always operate on the system clock (
φ
).
When the DTSPEED bit in SBYCR or the EXCKS bit in BCSR2 is set to 1, the
φ
clock can be
used as the DTC/RFU operating clock or external extended area bus cycle clock.
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.
By clearing all of bits SCK2 to SCK0 to 0, a transition is made to high-speed mode 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 the 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 set to 1, the LSON bit cleared to 0, and the PSS bit in TCSR (WDT_1) cleared to 0,
operation shifts to 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 27.2 shows an example of medium-speed mode timing.
Summary of Contents for H8S/2158
Page 10: ...Rev 3 00 Jan 25 2006 page viii of lii...
Page 36: ...Rev 3 00 Jan 25 2006 page xxxiv of lii B Product Lineup 863 C Package Dimensions 864 Index 865...
Page 47: ...Rev 3 00 Jan 25 2006 page xlv of lii Appendix Figure C 1 Package Dimensions TBP 112A 864...
Page 54: ...Rev 3 00 Jan 25 2006 page lii of lii...
Page 70: ...Section 1 Overview Rev 3 00 Jan 25 2006 page 16 of 872 REJ09B0286 0300...
Page 118: ...Section 3 MCU Operating Modes Rev 3 00 Jan 25 2006 page 64 of 872 REJ09B0286 0300...
Page 126: ...Section 4 Exception Handling Rev 3 00 Jan 25 2006 page 72 of 872 REJ09B0286 0300...
Page 198: ...Section 6 Bus Controller Rev 3 00 Jan 25 2006 page 144 of 872 REJ09B0286 0300...
Page 326: ...Section 10 8 Bit PWM Timer PWM Rev 3 00 Jan 25 2006 page 272 of 872 REJ09B0286 0300...
Page 440: ...Section 15 Watchdog Timer WDT Rev 3 00 Jan 25 2006 page 386 of 872 REJ09B0286 0300...
Page 606: ...Section 17 I 2 C Bus Interface IIC Rev 3 00 Jan 25 2006 page 552 of 872 REJ09B0286 0300...
Page 742: ...Section 19 Multimedia Card Interface MCIF Rev 3 00 Jan 25 2006 page 688 of 872 REJ09B0286 0300...
Page 750: ...Section 21 D A Converter Rev 3 00 Jan 25 2006 page 696 of 872 REJ09B0286 0300...
Page 768: ...Section 22 A D Converter Rev 3 00 Jan 25 2006 page 714 of 872 REJ09B0286 0300...
Page 770: ...Section 23 RAM Rev 3 00 Jan 25 2006 page 716 of 872 REJ09B0286 0300...
Page 824: ...Section 26 Clock Pulse Generator Rev 3 00 Jan 25 2006 page 770 of 872 REJ09B0286 0300...
Page 844: ...Section 27 Power Down Modes Rev 3 00 Jan 25 2006 page 790 of 872 REJ09B0286 0300...
Page 878: ...Section 28 List of Registers Rev 3 00 Jan 25 2006 page 824 of 872 REJ09B0286 0300...
Page 926: ...Index Rev 3 00 Jan 25 2006 page 872 of 872 REJ09B0286 0300...