Motorola MCF5281 사용자 설명서
MOTOROLA
Chapter 18. Watchdog Timer Module
18-5
Memory Map and Registers
18.5.2.3 Watchdog Count Register (WCNTR)
18.5.2.4 Watchdog Service Register (WSR)
When the watchdog timer is enabled, writing 0x5555 and then 0xAAAA to WSR before
the watchdog counter times out prevents a reset. If WSR is not serviced before the timeout,
the watchdog timer sends a signal to the reset controller module that sets the RSR[WDR]
bit and asserts a system reset.
the watchdog counter times out prevents a reset. If WSR is not serviced before the timeout,
the watchdog timer sends a signal to the reset controller module that sets the RSR[WDR]
bit and asserts a system reset.
Both writes must occur in the order listed before the timeout, but any number of instructions
can be executed between the two writes. However, writing any value other than 0x5555 or
0xAAAA to WSR resets the servicing sequence, requiring both values to be written to keep
the watchdog timer from causing a reset.
can be executed between the two writes. However, writing any value other than 0x5555 or
0xAAAA to WSR resets the servicing sequence, requiring both values to be written to keep
the watchdog timer from causing a reset.
Table 18-4. WMR Field Descriptions
Bit(s)
Name
Description
15–0
WM
Watchdog modulus. Contains the modulus that is reloaded into the watchdog counter by a
service sequence. Once written, the WM[15:0] field is not affected by further writes except in
halted mode. Writing to WMR immediately loads the new modulus value into the watchdog
counter. The new value is also used at the next and all subsequent reloads. Reading WMR
returns the value in the modulus register.
Reset initializes the WM[15:0] field to 0xFFFF.
Note: The prescaler counter is reset anytime a new value is loaded into the watchdog counter
and also during reset.
service sequence. Once written, the WM[15:0] field is not affected by further writes except in
halted mode. Writing to WMR immediately loads the new modulus value into the watchdog
counter. The new value is also used at the next and all subsequent reloads. Reading WMR
returns the value in the modulus register.
Reset initializes the WM[15:0] field to 0xFFFF.
Note: The prescaler counter is reset anytime a new value is loaded into the watchdog counter
and also during reset.
15
14
13
12
11
10
9
8
Field
WC15
WC14
WC13
WC12
WC11
WC10
WC9
WC8
Reset
1111_1111
R/W
R
7
6
5
4
3
2
1
0
Field
WC7
WC6
WC5
WC4
WC3
WC2
WC1
WC0
Reset
1111_1111
R/W
R
Address
IPSBAR + x0014_0004, 0x0014_0005
Figure 18-4. Watchdog Count Register (WCNTR)
Table 18-5. WCNTR Field Descriptions
Bit(s)
Name
Description
15–0
WC
Watchdog count field. Reflects the current value in the watchdog counter. Reading the 16-bit
WCNTR with two 8-bit reads is not guaranteed to return a coherent value. Writing to WCNTR
has no effect, and write cycles are terminated normally.
WCNTR with two 8-bit reads is not guaranteed to return a coherent value. Writing to WCNTR
has no effect, and write cycles are terminated normally.