56F8355_07 Datasheet, PDF (108/164 Pages) Freescale Semiconductor, Inc – 16-bit Digital Signal Controllers

set the bit, while writing a 1 to the bit will clear it.
6.5.2.4 External Reset (EXTR)—Bit 3
If 1, the EXTR bit indicates an external system reset has occurred. This bit will be cleared by a Power-On
Reset or by software. Writing a 0 to this bit position will set the bit, while writing a 1 to the bit position
will clear it. Basically, when the EXTR bit is 1, the previous system reset was caused by the external
RESET pin being asserted low.
6.5.2.5 Power-On Reset (POR)—Bit 2
When 1, the POR bit indicates a Power-On Reset occurred some time in the past. This bit can be cleared
only by software or by another type of reset. Writing a 0 to this bit will set the bit, while writing a 1 to the
bit position will clear the bit. In summary, if the bit is 1, the previous system reset was due to a Power-On
Reset.
6.5.2.6 Reserved—Bits 1–0
This bit field is reserved or not implemented. It is read as 0 and cannot be modified by writing.
6.5.3 SIM Software Control Registers (SIM_SCR0, SIM_SCR1, SIM_SCR2,
and SIM_SCR3)
Only SIM_SCR0 is shown below. SIM_SCR1, SIM_SCR2, and SIM_SCR3 are identical in functionality.
Base + $2 15 14 13 12 11 10 9
8
76
5
4
3210
Read
Write
FIELD
RESET
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Figure 6-5 SIM Software Control Register 0 (SIM_SCR0)
6.5.3.1 Software Control Data 1 (FIELD)—Bits 15–0
This register is reset only by the Power-On Reset (POR). It has no part-specific functionality and is
intended for use by a software developer to contain data that will be unaffected by the other reset sources
(RESET pin, software reset, and COP reset).
6.5.4 Most Significant Half of JTAG ID (SIM_MSH_ID)
This read-only register displays the most significant half of the JTAG ID for the chip. This register reads
$01F4.
56F8355 Technical Data, Rev. 12
108
Freescale Semiconductor
Preliminary