MMC2107 Datasheet, PDF (279/618 Pages) –

Freescale Semiconductor, Inc.
Watchdog Timer Module
Memory Map and Registers
13.6.2.4 Watchdog Service Register
When the watchdog timer is enabled, writing 0x5555 and then 0xAAAA
to the watchdog service register (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 which sets
the 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.
Address: 0x00c7_0006 and 0x00c7_0007
Bit 15
14
13
12
11
10
9
Bit 8
Read:
WS15 WS14 WS13 WS12 WS11 WS10 WS9
WS8
Write:
Reset: 0
0
0
0
0
0
0
0
Bit 7
6
5
4
3
2
1
Bit 0
Read:
WS7
WS6
WS5
WS4
WS3
WS2
WS1
WS0
Write:
Reset: 0
0
0
0
0
0
0
0
Figure 13-5. Watchdog Service Register (WSR)
MMC2107 – Rev. 2.0
MOTOROLA
Watchdog Timer Module
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Technical Data
279