SM8521 Datasheet, PDF (28/56 Pages) Sharp Electrionic Components – 8-Bit Single-Chip Microcomputer

SM8521
Table 4 System State at Standby Mode
Transition method
Wake up method
CPU
Main-clock
Sub-clock
RAM, register
I/O port
Function
Timer
blocks
Capture trigger
UART
HALT MODE
HALT instruction execution
Hardware reset, interrupt
Stop
Operating
Operating
Remain^∗2
Remain (interruptable)
Operating
Operating
Operating
STOP MODE
STOP instruction execution
Hardware reset, interrupt^∗1
Stop
Stop
Operating
Remain^∗2
Remain (interruptable)
The timer used main-clock as counter clock is stop. It
used external clock as counter clock can still operate.
Stop
Stop
LCDC
Waveform
Operating
Operating
generator
∗1 The interrupts used to wake up the chip from STOP
mode only have the external interrupts and the internal
interrupts generated by operatable Timer, and SIO.
Stop
Stop
∗2 General registers, control registers, and the other
memory content all are remained. But something will be
changed for the operatable blocks at STOP mode (for
example, interrupt flag register IR0, IR1 content, etc.)
ABOUT HOU TO USE HALT MODE AND STOP MODE
The chip switches back to the operating mode from
the HALT mode immediately after the wake up
sources are encountered. For this reason, the
HALT mode is more suitable for systems that need
to be immediately woke up frequently. And, all
interrupt sources (other than illegal instruction trap)
can wake up the chip from the HALT mode.
Switching back to the operating mode from the
STOP mode after the wake up sources are
encountered must pass a warming up period. In
addition, the function blocks used by the main-clock
cannot be used in the wake up from STOP mode.
Since the sampling circuit is stopped, it can not
accept the PINT0 input, either.
For this reason, the STOP mode (conserving more
power than the HALT mode) is suitable for systems
that can easily support the longer time that it will
take to get, back to the operating mode (warming
up period) .
In standby mode, I/O ports setting and output level
for output ports are remained.
Before switches to standby mode, in order to
reduce to the current through every pins, set with
program.
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