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EM78P312N
8-Bit Microcontroller
Product Specification (V1.0) 10.03.2006
• 23
(This specification is subject to change without further notice)
5.4 CPU Operation Mode
Registers for CPU Operation Mode
R_BANK Address NAME Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Bank 0 0X05 SCR 0 PS2 PS1 PS0 0 1 SIS REM
− − − − R/W R/W R/W − − R/W R/W
* R_BANK: Register Bank (Bits 7, 6 of R3), R/W: Read/Write
Normal Mode
CPU : Operating
Fosc: Oscillates
Reset Occurs
SIS=0 + SLEP
Sleep Mode
CPU : Halts
Fosc: Stops
Idle Mode
CPU : Halts
Fosc: Oscillates
Interrupt
SIS=1 + SLEP
/SLEEP Pin Input
Fig. 5-4 Operation Mode and Switching
Table 2. Mode Switching Control
Mode Switch Switch Method Note
Normal Æ Sleep Set SIS = 1, execute SLEP instruction −
Sleep Æ Normal /SLEEP pin wake up −
Normal Æ Idle Set SIS = 0, execute SLEP instruction −
Idle Æ Normal Interrupt −
Table 3. Operation Mode
Operation Mode Frequency CPU Code
On-chip
Peripherals
Reset Reset Reset
Normal Fosc
Idle
Turn on
Fosc
Signal
Clock
Sleep Turn off
Halt
Halt
In Normal mode, the CPU core and on-chip peripherals operate in oscillator frequency.
In Idle mode, the CPU core halts, but the on-chip peripheral and oscillator circuit remain
active. Idle mode is released to Normal mode by any interrupt source. If the ENI
instruction is set, an interrupt will be serviced first followed by executing the next
instruction which is after the Idle mode is released and the interrupt service is finished.
If the ENI instruction is not set, the next instruction will be executed which is after the
Idle mode start instruction. Idle mode can also be released by setting the /RESET pin
to low and executing a reset operation.