NEC PD750004 Manuale Utente

µPD750008 USER'S MANUAL

For the standby function of the µPD750008, either of the following two values can be selected by a mask

option as the wait time during which the start of oscillation deferred from the generation of a RESET signal:

<1> 2

17

/f

X

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

<2> 2

15

/f

X

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

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

15

/f

X

.

When the standby modes are used, the following steps are used.

<1> Detect a standby mode setting factor such as power removal on an interrupt input or port input.  (INT4

is useful for power removal detection.)

<2> Configure I/O ports for minimum current drain.

<3> Specify interrupts for releasing a standby mode.  (INT4 is useful.  All interrupt enable flags not used

for release are to be cleared.)

<4> Specify an operation to be performed after release. (IME is to be manipulated according to whether

interrupt processing is performed or not.)

<5> Specify a CPU clock to be used after release.  (If the CPU clock is changed, required machine cycles

must elapse before the standby mode is set.)

<6> Select a wait time to be used when a standby mode is released.

<7> Set a standby mode using a STOP or HALT instruction.

A standby mode when combined with the system clock switch function enables a lower power consumption

and lower-voltage operation.

• The STOP mode is set on the falling edge of INT4, and is released on the rising edge of INT4.  (INTBT

is not used.)

• All I/O ports have a high impedance.

• The INT0 and INTT0 interrupts are used for the program, but are not used to release the STOP mode.

• After the STOP mode is released, interrupts are enabled.

• After the STOP mode is released, the lowest-speed CPU clock is used for operation.  Then, the CPU

clock is changed to the high-speed one after 250 ms.

• A wait time used when the STOP mode is released is about 31.3 ms.

• After the STOP mode is released, another wait time of 31.3 ms is used for stable power supply operation.

The P00/INT4 pin is checked twice to remove chattering.