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M16C/64C Group
7.3
Optional Function Select Area
In the optional function select area, the MCU state after reset and the function to prevent rewrite in parallel
I/O mode are selected.
The optional function select area is not an SFR, and therefore cannot be rewritten by a program. Set an
appropriate value when writing a program to flash memory. The entire optional function select area
becomes FFh when the block including the optional function select area is erased.
In blank products, the OFS1 address value is FFh when shipped. After a value is written by the user, this
address takes on the written value.
In programmed products, the OFS1 address value is the value set in the user program prior to shipping.
Selection using the optional function select area can be used in single-chip mode or memory expansion
mode. The option function select area cannot be used in microprocessor mode. When using the MCU in
microprocessor mode, clear the internal ROM.
7.3.1
Optional Function Select Address 1 (OFS1)
Optional Function Select Address 1
b7
b6 b5 b4
b3
1
VDSEL1 (Vdet0 select bit 1) (b5)
The Vdet0 level used in voltage detector 0 is selectable. Voltage detector 0 operates based on Vdet0.
Set the VDSEL1 bit to 0 (Vdet0_2) when using power-on reset or voltage monitor 0 reset. Refer to
6.4.10 "Cold/Warm Start Discrimination".
This bit is enabled in single-chip mode, while disabled in boot mode.
LVDAS (Voltage detector 0 start bit) (b6)
When using power-on reset, set this bit to 0 (voltage monitor 0 reset enabled after hardware reset).
This bit is enabled in single-chip mode, while disabled in boot mode.
R01UH0092EJ0110 Rev.1.10
Jul 31, 2012
b2
b1
b0
Symbol
1
OFS1
Bit Symbol
WDTON
Watchdog timer start select bit
—
Reserved bit
(b1)
ROMCR
ROM code protect cancel bit
ROMCP1 ROM code protect bit
—
Reserved bit
(b4)
VDSEL1
Vdet0 select bit 1
LVDAS
Voltage detector 0 start bit
After-reset count source
CSPROINI
protection mode select bit
Address
FFFFFh
Bit Name
0 : Watchdog timer starts automatically
after reset
1 : Watchdog timer is stopped after reset
Set to 1.
0 : ROM code protection cancelled
1 : ROMCP1 bit enabled
0 : ROM code protection enabled
1 : ROM code protection disabled
Set to 1.
0 : Vdet0_2
1 : Vdet0_0
0 : Voltage monitor 0 reset enabled
after hardware reset
1 : Voltage monitor 0 reset disabled
after hardware reset
0 : Count source protection mode
enabled after reset
1 : Count source protection mode
disabled after reset
7. Voltage Detector
Function
Page 72 of 807
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