TMC8462 Datasheet • Document Revision V1.4 • 2018-May -09
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7.19 MFC IO Watchdog Block
General Function The watchdog timer allows monitoring of external signals, or monitoring of EtherCAT
activity. A certain condition can be chosen for retriggering the watchdog, i.e. a certain input signal
constellation. In case this constellation does not occur at least once within a pre-programmable time
period, the watchdog timer will expire and will trigger a certain watchdog action.
To avoid static reset of the watchdog, the watchdog input condition is edge sensitive, i.e. it becomes reset
when the condition goes active respectively goes inactive. Once the watchdog expires, the watchdog safety
circuitry becomes active. This action can bring I/O lines into a certain state, in order to allow the system to
return to a known, safe condition. Therefore, all I/O lines are directly mapped to the GPIO ports of the
chip, so that they perform independently of the actually configured peripheral configuration.
The watchdog action can be chosen to remain active continuously, until it becomes reset by a watchdog
re-configuration, or it can be programmed to return to normal operation state, once the selected condition
becomes true again.
In an optional use case, the watchdog timer can be used to measure the maximum delay in between of
the occurrence of certain input conditions, in between of SPI frames, etc.
The watchdog unit finds itself between the MFC IO crossbar and the IO pads as shown in Figure 49. Thus,
the watchdog monitors the 24 MFCIOxx signals. Depending on the crossbar mapping these signals are
either inputs or outputs. Their logical function depends on the crossbar mapping to/from the MFC IO
functional sub-blocks.
Figure 49: Logical position of the MFC IO watchdog unit between crossbar and MFCIOxx pins
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