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PXA300 Processor and PXA310 Processor
Vol. I: System and Timer Configuration Developers Manual
Doc. No. MV-TBD-00 Rev. A
CONFIDENTIAL
Copyright © 12/13/06 Marvell
Page 240
Document Classification: Proprietary Information
December 13, 2006
Not approved by Document Control. For review only.
Figure 9-2. Application Subsystem Reset Distribution
9.2.1.1
System Reset
System reset is invoked when:
•
a positive power-supply assertion is detected on the back-up battery pin VCC_BBATT following a
powered-off condition or
•
when the nRESET pin is asserted or
•
when the processor watchdog reset is asserted
System reset causes all units including the BPMU to reset to the same known state.
9.2.1.1.1
Behavior During System Reset
During system reset, all internal registers and processes are held at their defined reset conditions. When system
reset is entered, the only activity inside the subsystems is the stabilization of the timekeeping oscillator. The
remaining internal clocks are stopped, and the chip is fully static.
Normal boot-up sequencing begins with all units in the application subsystem starting with their predefined reset
conditions. Core software must examine the
“Application Subsystem Reset Status Register (ARSR)”
(see
) to determine if the reset source was a system reset.
9.2.1.2
GPIO Reset
GPIO reset is invoked when the nGPIO_RESET pin is asserted low for more than a specified period of time. The
nGPIO_RESET detection itself is transparent to the BPMU; the services unit communicates the occurrence of
the GPIO reset to the BPMU although software executing in application subsystem can initiate a GPIO reset. See
for more information.
Refer to the PXA300 Processor and PXA310 Processor Electrical, Mechanical, and Thermal Specification for
timing requirements.
9.2.1.2.1
Behavior During GPIO Reset
During GPIO reset, all units are held at their defined reset conditions. The only exception is the external DDR
memory whose contents are preserved through the GPIO reset. The BPMU undertakes special actions to achieve
this data integrity as explained in
.
Power-On Reset
Hardware Reset
Watchdog Reset
GPIO Reset
Low-power State Exit Reset
Application Subsystem System Reset
Application Subsystem Low-power State Exit
Reset
Application Subsystem GPIO
Reset
Application Subsystem System
Reset