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CHAPTER 3 CPU AND CONTROL UNITS
■ Low-power Consumption Modes
This section describes the individual low-power consumption modes of the MB91260B series and explains
how to use them.
The MB91260B series has the following low-power consumption modes:
•
Sleep mode
The device enters the sleep state in response to a register write.
•
Stop mode
The device enters the stop state in response to a register write.
Each of these modes is detailed below.
●
Sleep mode
Writing "1" to the SLEEP bit (bit6) in the STCR (standby control register) establishes the sleep mode and
causes the device to enter the sleep state. The device remains in the sleep state until a sleep-state return
source (an event that triggers the device to return from the sleep state) is generated.
For information about the sleep state, see "● Sleep state" of the section 3.12 "Device Status Control" as
well.
[Transition to sleep mode]
For transition to sleep mode, select the synchronous standby mode (using the SYNCS bit (bit8) in the
TBCR (timebase counter control register)) and be sure to use the following sequence:
/* Writing STCR */
ldi
ldi
stb
/* Writing STBR */
ldi
ldi
stb
ldi
stb
/* Clearing the time base counter in here */
ldub
/* Starting synchronous standby transition */
ldub
nop
nop
nop
nop
nop
If "1" is written to both of this bit and the STOP bit (bit7) in the STCR (standby control register), the STOP
bit (bit7) overrides the other, causing the transition to the stop state.
96
#_STCR, R0
#Val_of_Stby, rl
rl,@r0
#_CTBR, r2
#0xA5, rl
rl,@r2
#0xA5, rl
rl,@r2
@r0, rl
@r0, rl
; STCR register (0x0481)
; Val_of_Stby is the write data to STCR.
; Writing to STCR
; CTBR register (0x0483)
; Clear command (1)
; Writing A5 to CTBR
; Clear command (2)
; Writing A5 to CTBR
; Reading STCR
; Reading dummy STCR
; NOP × 5 for timing adjustment
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