MC9S12XD256CAL Datasheet, PDF (95/1348 Pages) Freescale Semiconductor, Inc – This specification describes the function of the clocks and reset generator (CRG).

Chapter 2 Clocks and Reset Generator (S12CRGV6)
Table 2-9. COPCTL Field Descriptions (continued)
Field
Description
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 COPCTL register. It is intended for BDM writing the RSBCK without touching the contents of
WCOP and CR[2:0].
0 Write of WCOP and CR[2:0] has an effect with this write of COPCTL
1 Write of WCOP and CR[2:0] has no effect with this write of COPCTL. (Does not count for “write once”.)
2–0
CR[1:0]
COP Watchdog Timer Rate Select — These bits select the COP time-out rate (see Table 2-10). The COP
time-out period is OSCCLK period divided by CR[2:0] value. 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) reinitializing the COP counter via the ARMCOP 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 emulation or special modes
Table 2-10. COP Watchdog Rates¹
CR2
CR1
CR0
OSCCLK
Cycles to Time-out
0
0
0
COP disabled
0
0
1
2¹⁴
0
1
0
2¹⁶
0
1
1
2¹⁸
1
0
0
2²⁰
1
0
1
2²²
1
1
0
2²³
1
1
1
2²⁴
1 _{OSCCLK cycles are referenced from the previous COP time-out reset}
(writing 0x_55/0x_AA to the ARMCOP register)
MC9S12XDP512 Data Sheet, Rev. 2.21
Freescale Semiconductor
95