MC9S08RC8 Datasheet, PDF (68/234 Pages) Freescale Semiconductor, Inc – Microcontrollers

Resets, Interrupts, and System Configuration
5.8.4 System Options Register (SOPT)
This register may be read at any time. Bits 3 and 2 are unimplemented and always read 0. This is a
write-once register so only the first write after reset is honored. Any subsequent attempt to write to SOPT
(intentionally or unintentionally) is ignored to avoid accidental changes to these sensitive settings. SOPT
must be written during the user’s reset initialization program to set the desired controls even if the desired
settings are the same as the reset settings.
R
W
Reset
7
COPE
1
6
5
4
3
2
COPT
STOPE
0
0
1
0
1
0
0
= Unimplemented or Reserved
Figure 5-5. System Options Register (SOPT)
1
BKGDPE
0
RSTPE
1
1
Table 5-5. SOPT Field Descriptions
Field
Description
7
COPE
6
COPT
5
STOPE
1
BKGDPE
0
RSTPE
COP Watchdog Enable — This write-once bit defaults to 1 after reset.
0 COP watchdog timer disabled.
1 COP watchdog timer enabled (force reset on timeout).
COP Watchdog Timeout — This write-once bit defaults to 1 after reset.
0 Short timeout period selected (2¹⁸ cycles of BUSCLK).
1 Long timeout period selected (2²⁰ cycles of BUSCLK).
Stop Mode Enable — This write-once bit defaults to 0 after reset, which disables stop mode. If stop mode is
disabled and a user program attempts to execute a STOP instruction, an illegal opcode reset is forced.
0 Stop mode disabled.
1 Stop mode enabled.
Background Debug Mode Pin Enable — The BKGDPE bit enables the PTD0/BKGD/MS pin to function as
BKGD/MS. When the bit is clear, the pin will function as PTD0, which is an output only general purpose I/O. This
pin always defaults to BKGD/MS function after any reset.
0 BKGD pin disabled.
1 BKGD pin enabled.
RESET Pin Enable — The RSTPE bit enables the PTD1/RESET pin to function as RESET. When the bit is clear,
the pin will function as PTD1, which is an output only general purpose I/O. This pin always defaults to RESET
function after any reset.
0 RESET pin disabled.
1 RESET pin enabled.
MC9S08RC/RD/RE/RG Data Sheet, Rev. 1.11
68
Freescale Semiconductor