CHAPTER 8 CLOCK GENERATOR FUNCTIONS
User’s Manual U12688EJ4V0UM00
243
(2) Releasing software STOP mode
The software STOP mode is released by NMI pin input or RESET pin input.
Also, when releasing the software STOP mode in the PLL mode and the oscillator connection mode (CESEL
bit of the PSC register = 0), it is necessary to secure oscillation stabilization time for the oscillator.
Note that depending on the program, PLL lockup time may also be necessary. For details, refer to 8.4 PLL
Lockup.
(a) Release by NMI Pin Input
An NMI pin input is acknowledged as an NMI request as well as a release of the software STOP mode.
However, if setting in the software STOP mode is included in an NMI processing routine, the software
STOP mode only is released and the interrupt is not acknowledged. The interrupt request itself is held
pending.
The interrupt processing started when the STOP mode is released by an NMI pin input is treated in the
same way as ordinary NMI interrupt processing in an emergency, etc. (since the NMI interrupt handler
address is unique). Consequently, in cases where it is necessary to distinguish between the two, it is
necessary to prepare the software status in advance and set the status before setting the PSC register
using the store instruction or a bit operation instruction. By checking this status in NMI interrupt
processing, it is possible to distinguish it from an ordinary NMI.
(b) Release by RESET Pin Input
This is the same as an ordinary reset operation.
8.5.6 Clock output inhibit mode
If the DCLK0 bit and DCLK1 bit of the PSC register are set to 1, the system enters the clock output inhibit mode, in
which clock output from the CLKOUT pin is disabled.
This is most appropriate in single-chip mode 0 and 1 systems, or in systems which access instruction fetches or
data from external expansion devices asynchronously.
In this mode, since the CLKOUT signal output’s operation is completely stopped, much lower power consumption
and suppression of radiation noise from the CLKOUT pin is possible. Also, by combining this mode with the HALT,
IDLE, and software STOP mode, more effective power saving becomes possible (refer to 8.5.2 Control registers).
(Fixed at the low level)
L
CLKOUT
(During normal
operation)
CLKOUT
(in the clock
output inhibit
mode)
Remark
When in flash memory programming mode, the CLKOUT signal is not output regardless of the PSC
register setting.
Содержание V850E/MS1 UPD703100
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