NEC PD750004 Manuale Utente

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CHAPTER 7 STANDBY FUNCTION

Caution

2. Reset all the interrupt request flags before setting the standby mode. If an interrupt

source whose interrupt request flag and interrupt enable flag are both set exists, the

initiated standby mode is released immediately after it is set (see Figure 6-1). When

the STOP mode is set, however, the µPD750008 enters the HALT mode immediately

after the STOP instruction is executed, then returns to the operation mode after the

wait time specified by the BTM register has elapsed.

7.2 RELEASE OF THE STANDBY MODES

The STOP mode and HALT mode are released by a RESET signal or the generation of an interrupt request

signal that is enabled with the interrupt enable flag. Figure 7-1 shows how the STOP and HALT modes are

released.

Figure 7-1. Standby Mode Release Operation (1/2)

(a) Release of the STOP mode by RESET signal

(b) Release of the STOP mode by the occurrence of an interrupt

Note The following two wait times can be selected by a mask option:

(21.8 ms at 6.00 MHz, 31.3 ms at 4.19 MHz)

(5.46 ms at 6.00 MHz, 7.81 ms at 4.19 MHz)

However, the µPD75P0016 does not have a mask option and its wait time is fixed to 2

Remark The dashed line indicates the case where the interrupt request that releases the standby mode

is accepted.

STOP instruction

Standby
release
signal

Clock

Operating
mode

STOP mode

HALT mode

Operating
mode

No oscillation

Oscillation

Wait

(Time set by BTM)

STOP instruction

Wait

RESET
signal

Clock

Operating
mode

STOP mode

HALT mode

Operating
mode

No oscillation

Oscillation

Note