
GR716-DS-UM, May 2019, Version 1.29
87
www.cobham.com/gaisler
GR716
voltage instant peak level provided on the package pins for each supply, respectively. Otherwise,
undesired Brownout detections giving inadvertent system shutdowns can result. Note however that
the Brownout detectors have a spurious-pulse rejection filter of about 5us.
Furthermore, for any supply voltage in the system that is equipped with a reset threshold detection,
such as the on-chip VDD_CORE detector or any arbitrary supply detector on PCB, the Brownout
level must be set with a certain margin higher than the reset level, such that there is enough time to
ensure that the Brownout interrupt routine can be executed before the reset is activated. Therefore, the
selection of the Brownout threshold levels should be extra carefully co-designed with the power-sup-
ply and reset designs on PCB, in Microcontroller applications that will utilize the Brownout detectors
on supply voltages that are also reset detected (which the VDD_CORE always is).
The Brownout detection is latched in the interrupt handling logic, and the detected event can then be
taken care of by the interrupt service routine.
After power-on reset, the Microcontroller starts with all Brownout interrupt mask bits set to enable.
8.2.3
Reset IO control
The 64 General purpose IO described in chapter 2.4 and 2.5 is forced to high impedance mode when
core voltage supply is lower than the threshold for releasing the system reset.
8.2.4
Brownout IO control
The control register for the 64 General purpose IO described in chapter 2.4 and 2.5 described in chap-
ter Configuration Registers can be forced by the system to keep its state when Brown Out has been
detected for at least one of the external voltage supplies, VDD_CORE, VDD_IO, VDDA_PLL,
VDDA_ADC, VDDA_DAC, VDD_LVDS, VDDA_REF.
The system can force all 64 General purpose IO by disabling clock source #23 described in section 26
8.2.5
Access control
The reset release time is programmable by an external capacitor, C_RST. Capacitor value and release
time is specified in section 52.10
Brown Out detection level and interrupt generation can be controlled via registers.
8.3
Registers
The Reset Generation and Brownout Detection is programmed through registers mapped into APB
address space.
Table 67.
Reset Generation and Brownout Detection status and control registers
APB address offset
Register
0x00
Configuration register
0x04
Status register
0x08
Interrupt register
0x0C
Interrupt mask register
0x10
LDO trim register
0x14
Voltage monitor delay register
0x18
Voltage monitor powerdown register
0x1C
Unused
0x20
Power control, XO and LVDS driver enable register
0x24
Brown Out disable IO from local register