CHAPTER 6 CLOCK GENERATION FUNCTION
User’s Manual U13850EJ6V0UD
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6.4.2 HALT mode
(1) Settings and operating states
In this mode, the clock’s oscillator continues to operate but the CPU’s operating clock is stopped. A clock
continues to be supplied for other on-chip peripheral functions to maintain operation of those functions. When
HALT mode is set while the CPU is idle, it enables the system’s total power consumption to be reduced.
In HALT mode, execution of programs is stopped but the contents of all registers and on-chip RAM are retained
as they were just before HALT mode was set. In addition, all on-chip peripheral functions that do not depend on
instruction processing by the CPU continue operating.
HALT mode can be set by executing the HALT instruction. It can be set when the CPU is operating on the main
clock.
The operating statuses in the HALT mode are listed in Table 6-1.
(2) Release of HALT mode
HALT mode can be released by an NMI request, an unmasked maskable interrupt request, or RESET input.
(a) Release by interrupt request
HALT mode is released regardless of the priority level when an NMI request or an unmasked maskable
interrupt request occurs. However, the following occurs if HALT mode was set as part of an interrupt
servicing routine.
(i)
Only HALT mode is released when an interrupt request that has a lower priority level than the interrupt
currently being serviced occurs, and the lower-priority interrupt request is not acknowledged. The
interrupt request itself is retained.
(ii)
When an interrupt request (including NMI request) that has a higher priority level than the interrupt
currently being serviced occurs, HALT mode is canceled and the interrupt request is acknowledged.
(b) Release by RESET pin input
This is the same as for normal reset operations.
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