Datasheet
SAM9G20
DS60001516A-page 18 2017 Microchip Technology Inc.
5. I/O Line Considerations
5.1 JTAG Port Pins
TMS, TDI and TCK are schmitt trigger inputs and have no pull-up resistors.
TDO and RTCK are outputs, driven at up to VDDIOP, and have no pull-up resistor.
The JTAGSEL pin is used to select the JTAG boundary scan when asserted at a high level. It integrates a permanent pull-down resistor
of about 15 kΩ to GND, so that it can be left unconnected for normal operations.
The NTRST signal is described in Section 5.3 “Reset Pins”.
All the JTAG signals are supplied with VDDIOP.
5.2 Test Pin
The TST pin is used for manufacturing test purposes when asserted high. It integrates a permanent pull-down resistor of about 15 kΩ to
GNDBU, so that it can be left unconnected for normal operations. Driving this line at a high level leads to unpredictable results.
This pin is supplied with VDDBU.
5.3 Reset Pins
NRST is an open-drain output integrating a non-programmable pull-up resistor. It can be driven with voltage at up to VDDIOP.
NTRST is an input which allows reset of the JTAG Test Access port. It has no action on the processor.
As the product integrates power-on reset cells, which manages the processor and the JTAG reset, the NRST and NTRST pins can be left
unconnected.
The NRST and NTRST pins both integrate a permanent pull-up resistor of 100 kΩ minimum to VDDIOP.
The NRST signal is inserted in the Boundary Scan.
5.4 PIO Controllers
All the I/O lines are Schmitt trigger inputs and all the lines managed by the PIO Controllers integrate a programmable pull-up resistor of
75 kΩ typical with the exception of P4–P31. For details, refer to Section 40. “Electrical Characteristics”. Programming of this pull-up resistor
is performed independently for each I/O line through the PIO Controllers.
5.5 I/O Line Drive Levels
The PIO lines drive current capability is described in Section 40.2 “DC Characteristics”.
5.6 Shutdown Logic Pins
The SHDN pin is a tri-state output only pin, which is driven by the Shutdown Controller. There is no internal pull-up. An external pull-up to
VDDBU is needed and its value must be higher than 1 MΩ.. The resistor value is calculated according to the regulator enable implemen-
tation and the SHDN level.
The pin WKUP is an input-only. It can accept voltages only between 0V and VDDBU.