Direct Transitions; 22.11.1 Overview Of Direct Transitions; Clock Output Disabling Function - Hitachi H8S/2646 Hardware Manual

Hitachi 16-bit single-chip microcomputer h8s/2646 series

Table of Contents

Direct Transitions

There are three modes, high-speed, medium-speed, and sub-active, in which the CPU executes

programs. When a direct transition is made, there is no interruption of program execution when

shifting between high-speed and sub-active modes. Direct transitions are enabled by setting the

LPWRCR DTON bit to 1, then executing the SLEEP instruction. After a transition, direct

transition interrupt exception processing starts.

Direct Transitions from High-Speed Mode to Sub-Active Mode: Execute the SLEEP

instruction in high-speed mode when the SBYCR SSBY bit = 1, LPWRCR LSON bit = 1, and

DTON bit = 1, and TSCR (WDT1) PSS bit = 1 to make a transition to sub-active mode.

Direct Transitions from Sub-Active Mode to High-Speed Mode: Execute the SLEEP

instruction in sub-active mode when the SBYCR SSBY bit = 1, LPWRCR LSON bit = 0, and

DTON bit = 1, and TSCR (WDT1) PSS bit = 1 to make a direct transition to high-speed mode

after the time set in SBYCR STS2 to STS0 has elapsed.

ø Clock Output Disabling Function

Output of the ø clock can be controlled by means of the PSTOP bit in SCKCR, and DDR for the

corresponding port. When the PSTOP bit is set to 1, the ø clock stops at the end of the bus cycle,

and ø output goes high. ø clock output is enabled when the PSTOP bit is cleared to 0. When DDR

for the corresponding port is cleared to 0, ø clock output is disabled and input port mode is set.

Table 22-6 shows the state of the ø pin in each processing state.

Table 22-6 ø Pin State in Each Processing State

Hardware standby mode

Software standby mode, watch

mode, and direct transition

Sleep mode and sub-sleep mode

High-speed mode, medium-speed

Sub-active mode

High impedance

High impedance

High impedance

High impedance