ZAMC4100 Datasheet, PDF (36/155 Pages) Integrated Device Technology – Actuator and Motor Controller

ZAMC4100 Datasheet
Figure 3.3 ZAMC4100 Reset Sources
sys_rst
WDT
mcu_rst
POR
PORF
OVT
PWRT
tPWRT
SBC clock
SLEEP
WDTSYSF
STBY
WDTMCUF
OVTIF
DRIVERS
RSTN
SBC
RSTN
MCU
RSTN
Power-on-Reset (POR)
This global system reset is generated when the supply at the VDDE pin crosses the voltage thresholds specified
in Table 1.5.
WDT Reset
There are two types of watchdog timer resets: the MCU reset and the global system reset. In the event of an
abnormal condition in which the MCU fails to periodically clear the WDT counter, the WDT will attempt to reset the
MCU. However after a configurable number of consecutive MCU resets, the WDT will invoke a global system
reset where both the SBC and MCU will be re-initialized.
OVT Drivers Control Reset
The over-temperature (OVT) reset is generated if the SBC chip temperature reaches the value specified by the
parameter OVT_TH (125ºC; see Table 1.5). If an OVT reset occurs, it clears all drivers’ control registers. From a
functional point of view, the OVT reset is equivalent to a shut-down signal for the drivers. It is implemented in a
way that ensures that the drivers shut down even if the system clock is not present.
The driver control registers that are reset by an OVT reset event are HBDCTRL (Table 3.13), HBDDIAG (Table
3.17), HSDCTRL (Table 3.20), and ECMCTRL (Table 3.27). The OVT reset does not influence the MCU or the
other SBC registers. If an OVT event has taken place, it is indicated in interrupt flag OVTIF of register RSTSTAT
(see Table 3.1), and if interrupt by OVT is enabled (bit OVTIE = 1), the IRQN line is forced low.
In order to recover from an OVT event (i.e., to enable the drivers again), the MCU software should first clear
interrupt flag OVTIF and then write the driver control registers again. As soon as the OVT event is active, the
driver control registers are kept in reset; i.e., the drivers cannot be enabled. In order to ensure that the OVT event
has been resolved, the MCU should try to clear OVTIF and re-check the flag. Successfully clearing OVTIF means
that the chip has cooled-down to a temperature below 125°C; i.e., it will be possible to re-enable the drivers. As
an additional step before re-enabling the drivers, it is recommended that the MCU measures the internal chip
temperature (using the ADC). This avoids enabling the drivers when the SBC temperature is close to 125°C (e.g.,
120°C) and as a result, the chip goes in OVT again a short time after the drivers are enabled.
© 2016 Integrated Device Technology, Inc.
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January 26, 2016