hd64338023s Renesas Electronics Corporation., hd64338023s Datasheet - Page 272

• Manufacturer Part Number: hd64338023s
• Description: Renesas 8-bit Single-chip Microcomputer Super Low Power Series
• Manufacturer: Renesas Electronics Corporation.

Section 8 I/O Ports
Bit 3— P9
Bit 3 turns the P9
and H8/38124 Group.
Bit 3
PIOFF
0
1
Note: In the H8/38024 ZTAT version and mask ROM version, and the HD64F38024R, the
Rev. 7.00 Mar 10, 2005 page 230 of 652
REJ09B0042-0700
following precautions should be followed when accessing the PIOFF bit.
When turning the voltage boost circuit on or off, always write to the register when the buffer
NMOS is off (port data set to 1). Also, when turning on the voltage boost circuit, first clear
PIOFF to 0 and then after waiting 30 system clock cycles turn on the buffer NMOS (port
data cleared to 0). If 30 system clock cycles have not elapsed the voltage boost circuit will
not start operating and it will not be possible to produce a large current flow, resulting in
unstable operation.
In the HD64F38024, the following precautions should be followed when accessing the
PIOFF bit.
In the HD64F38024, if port data bits are cleared from 1 to 0 while the PIOFF bit is set to 1,
repeated charge-discharge cycles will occur in the voltage boost circuit, causing the current
consumption to rise and fall cyclically. The amount of rise in the current consumption in this
case is between several tens of µA and 100 µA above the normal level. Therefore, the
following points should be kept in mind.
(1) Not Using Subclock
(2) Not Using Port 9
(3) Using Port 9 with PIOFF Always Cleared to 0
(4) Using Port 9 with PIOFF Set to 1
2
Regardless of whether or not port 9 is used, the PIOFF bit should be left at its initial
value (0) and not changed.
Port data should be used unchanged with the PIOFF bit either at its initial value (0) or
set to 1. In the latter case the current consumption will vary, due to the intermittent
operation of the voltage boost circuit, by about 1 µA (standby mode or watch mode, V
= 3.0 V, Ta = 25°C).
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.
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
to P9
Description
Large-current port step-up circuit is turned on
Large-current port step-up circuit is turned off
2
0
to P9
Step-Up Circuit Control (PIOFF)
0
step-up circuit on and off. This bit is reserved in the H8/38024S Group
(initial value)
CC