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CHAPTER 24 STANDBY FUNCTION
User’s Manual U12697EJ3V0UM
24.3 HALT Mode
24.3.1 Settings and operating states of HALT mode
The HALT mode is set by setting the HLT bit in standby control register (STBC) to 1.
STBC can be written in with 8-bit data by a special instruction. Therefore, the HALT mode is specified by the MOV
STBC, #byte instruction.
When enable interrupts is set (IE flag in PSW is set to 1), specify three NOP instructions after the HALT mode
setting instruction (after the HALT mode is released). If this is not done, after the HALT mode is released, multiple
instructions may execute before interrupts are accepted. Unfortunately, the order relationship between the interrupt
process and instruction execution changes. Since problems caused by the changes in the execution order are
prevented, the measures described earlier are required.
The system clock when setting can be set to either the main system clock or the subsystem clock.
The operating states in the HALT mode are described next.
Содержание mPD784225 Series
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