Renesas H8/38024 Series, Hardware Manual

Page: 254 / 661

Rev. 6.00, 08/04, page 224 of 628
(3) Using Port 9 with PIOFF Always Cleared to 0
This case applies to instances in which the voltage boost circuit is used constantly to
generate a large current glow, or an increase in current consumption due to the
operation of the voltage boost circuit is permissible even in the standby mode or watch
mode (see (2) above). In this case the PIOFF bit should be left at its initial value (0) and
not changed.
(4) Using Port 9 with PIOFF Set to 1
This case applies to instances in which it is necessary to change the value of the PIOFF
bit due to operating conditions or where it is desirable to keep the PIOFF bit set to 1
because no large current is required (for example, shutting down the voltage boost
circuit to reduce current consumption in the watch mode). In this case, clear port data
from 1 to 0 only when the PIOFF bit is cleared to 0. Also, if a large current flow is
required, the PIOFF bit should be set to 1 and all the port data bits set to 1. Then clear
PIOFF to 0 and, after allowing 30 clock cycles to permit stabilization of the voltage
boost circuit, clear the port data bits to 0. If time is not provided to allow the voltage
boost circuit to stabilize, it will not be possible to produce a large current flow. There are
no such restrictions when setting port data bits from 0 to 1, regardless of the size of the
current flow. To shut down the voltage boost circuit, set PIOFF to 1 after programming
the port data bits. An example of the sequence of steps is provided below.
(Example Procedure) Shutting Down the in the Watch Mode without a Large Current
Flow to Port 9
Other operation
PIOFF = 0 (voltage boost circuit on)
PDR9 operation or other operation
PIOFF = 1 (voltage boost circuit off)
Execute SLEEP instruction
Watch mode
Cancel watch mode
Bit 2—Reserved
This bit is reserved; it can only be written with 0.