Low-Power Modes - Fujitsu FR60 Hardware Manual

CHAPTER 3 CPU AND CONTROL UNITS

3.13.2 Low-power Modes

This section describes the low-power modes, some MB91301 series states, and how to
use the low-power modes.
■ Low-power Modes
The FR family has the following low-power modes:
• Sleep mode:The device enters the sleep state due to writing to a register.
• Stop mode: The device enters the stop state due to writing to a register.
These modes are described below.
■ Sleep Mode
If "1" is set for bit6 (SLEEP bit) of the standby control register (STCR), sleep mode is initiated
and the device enters the sleep state. The sleep state is maintained until a source for return
from the sleep state is generated.
If "1" is set for both bit7 (STOP bit) and bit6 of the standby control register (STCR), bit7 (STOP
bit) has precedence and the device enters the stop state.
For more information about the sleep state, see "Sleep State" in Section "3.13.1 Device States
and State Transitions".
[Sleep mode transition]
Use the following sequences after using the synchronous standby mode (TBCR:Set by time
base counter control register bit8 SYNCS bit) when putting in the sleep mode.
/* Write to STCR */
ldi
ldi
stb
/* Write to CTBR */
ldi
ldi
stb
ldi
stb
/* Clear the time base counter at this point */
ldub
/* Start moving to synchronous standby mode */
ldub
nop
nop
nop
nop
nop
136
#_STCR, r0 ; STCR register (481
#Val_of_Stby, r1 ; "Val_of_Stby" is the data to be written to STCR.
r1, @r0 ; Write to STCR.
#_CTBR, r2 ; CTBR register (483
#0xA5, r1 ; Clear command (1)
r1, @r2 ; Write A5 to CTBR.
#0x5A, r1 ; Clear command (2)
r1, @r2 ; Write 5A to CTBR.
@r0, r1 ; Read from STCR.
@r0, r1 ; Dummy read from STCR.
; NOP for timing adjustment x 5
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