Signal Description
80
SPRUH22I – April 2012 – Revised November 2019
Copyright © 2012–2019, Texas Instruments Incorporated
System Control and Interrupts
1.1
Signal Description
lists the external signals of the system control module and describes the function of each.
The NMI signal is one of the peripheral functions for the PB7_GPIO15 signal, and functions as a GPIO
after reset. PB7_GPIO15 is under commit protection and requires a special process to be configured as
any alternate function or to subsequently return to the GPIO function. The Pin Mux/ Pin Assignment
column in
lists the GPIO options for the NMI signal. When the PJ7_GPIO63 pin is configured, it
can be used as an XCLKIN pin to provide a clock source to the CAN and USB modules on this device.
The PF2_GPIO34 pin can be used as XCLKOUT to monitor the PLL output clock when configured for
either the master subsystem or control subsystem as shown in
. For more information on
configuring GPIOs, see the
General-Purpose Input/Outputs (GPIOs)
chapter.
The remaining signals (fixed) have a fixed pin assignment and function. Please refer to the device data
manual for more details on the pin numbers.
Table 1-1. Signals for System Control and Clocks
Pin Functional
Name
Pin Name(refer
to datasheet for
pin numbers)
Pin Mux/ Pin Assignment
Description
Peripheral
Mode
Alternate Mode
Select
Core Select
NMI
PB7_GPIO15
4
0 (default)
Master (default)
Non-maskable interrupt
XCLKIN
PJ7_GPIO63
0 (default)
0 (default)
Master (default)
External oscillator input. This pin
feeds a clock from an external 3.3-V
oscillator to the internal USB PLL
module and to the CAN peripherals.
XCLKOUT
PF2_GPIO34
0
15
Master
External oscillator output. This pin
outputs a clock divided-down from
the internal PLL System Clock. The
divide ratio is defined in the
XPLLCLKCFG register.
Don't Care
3
Control
X1
Refer to the data
manual for pin
no.
Fixed
Fixed
Fixed
On-chip crystal-oscillator input. To
use this oscillator, a quartz crystal or
a ceramic resonator must be
connected across X1 and X2. In this
case, the XCLKIN path must be
disabled by bit 13 in the CLKCTL
register. If this pin is not used, it
must be tied to GND.
X2
Refer to the data
manual for pin
no.
Fixed
Fixed
Fixed
On-chip crystal-oscillator output. A
quartz crystal or a ceramic resonator
must be connected across X1 and
X2. If X2 is not used, it must be left
unconnected.
XRS
Refer to the data
manual for pin
no.
Fixed
Fixed
Fixed
Digital Subsystem Reset (in) and
Watchdog/Power-on Reset (out). In
most applications, it is recommended
that the XRS pin be tied with the
ARS pin.
ARS
Refer to the data
manual for pin
no.
Fixed
Fixed
Fixed
Analog subsystem Reset (in) and
Power-on Reset (out). In most
applications, it is recommended that
the ARS pin be tied with the XRS
pin.
TRST
Refer to the data
manual for pin
no.
Fixed
Fixed
Fixed
JTAG test reset with internal
pulldown
VREG18EN
Refer to the data
manual for pin
no.
Fixed
Fixed
Fixed
Internal 1.8-V VREG Enable/Disable
for VDD18. Pull low to enable the
internal 1.8-V voltage regulator
(VREG18), pull high to disable
VREG18.