NXP Semiconductors MC9S12G - Page 373

S12 Clock, Reset and Power Management Unit (S12CPMU)
MC9S12G Family Reference Manual Rev.1.27
NXP Semiconductors 375
Table 10-12. CPMUCOP Field Descriptions
Field Description
7
WCOP
Window COP Mode Bit — When set, a write to the CPMUARMCOP register must occur in the last 25% of the
selected period. A write during the first 75% of the selected period generates a COP reset. As long as all writes
occur during this window, $55 can be written as often as desired. Once $AA is written after the $55, the time-out
logic restarts and the user must wait until the next window before writing to CPMUARMCOP. Table 10-13 shows
the duration of this window for the seven available COP rates.
0 Normal COP operation
1 Window COP operation
6
RSBCK
COP and RTI Stop in Active BDM Mode Bit
0 Allows the COP and RTI to keep running in Active BDM mode.
1 Stops the COP and RTI counters whenever the part is in Active BDM mode.
5
WRTMASK
Write Mask for WCOP and CR[2:0] Bit — This write-only bit serves as a mask for the WCOP and CR[2:0] bits
while writing the CPMUCOP register. It is intended for BDM writing the RSBCK without changing the content of
WCOP and CR[2:0].
0 Write of WCOP and CR[2:0] has an effect with this write of CPMUCOP
1 Write of WCOP and CR[2:0] has no effect with this write of CPMUCOP.
(Does not count for “write once”.)
2–0
CR[2:0]
COP Watchdog Timer Rate Select — These bits select the COP time-out rate (see Table 10-13 and
Table 10-14). Writing a nonzero value to CR[2:0] enables the COP counter and starts the time-out period. A COP
counter time-out causes a System Reset. This can be avoided by periodically (before time-out) initializing the
COP counter via the CPMUARMCOP register.
While all of the following four conditions are true the CR[2:0], WCOP bits are ignored and the COP operates at
highest time-out period (2
24
cycles) in normal COP mode (Window COP mode disabled):
1) COP is enabled (CR[2:0] is not 000)
2) BDM mode active
3) RSBCK = 0
4) Operation in Special Mode
Table 10-13. COP Watchdog Rates if COPOSCSEL1=0
(default out of reset)
CR2 CR1 CR0
COPCLK
Cycles to Time-out
(COPCLK is either IRCCLK or
OSCCLK depending on the
COPOSCSEL0 bit)
0 0 0 COP disabled
001 2
14
010 2
16
011 2
18
100 2
20
101 2
22
110 2
23
111 2
24