Power Management
15-44
15.3.9 Reset Protocol
The OMAP5910 device system reset is accomplished with a combination of
hardware and software control. Individual components (or modules) can be
reset by software.
There are five different sources that can cause a system reset. Three of them
are internally generated, and two of them are input from the external pin.
These sources are: the cold reset (PWRON_RESET reset pin), the warm reset
(from either the MPU_RST pin or software-generated), and the watchdog
reset (MPU and DSP).
-
The PWRON_RESET signal must be asserted for at least two 32-kHz
clock periods to be recognized. PWRON_RESET indicates a power-on
reset of the device. When PWRON_RESET is asserted low, the internal
power on reset and warm reset of MPU are active low until the 12-MHz
clock (REF_CK) is on. Then power-on reset is released after 20 REF_
CK cycles, and warm reset is released after 30 additional cycles.
-
When the device is awake, MPU_RST controls the warm reboot of the
MPU. The external reset signal must be asserted for 30 REF_CK cycles
to be recognized. The reset signal is synchronized before feeding to the
reset manager module (RSTM) that generates the internal reset signals
within the OMAP5910 device. The internal reset is asserted for at least
64 REF_CK cycles, and that clock must be running when MPU_RST is
asserted.
Some configuration registers are only reset to their default values by certain
types of resets:
The following registers are only reset by power-on reset:
-
ULPD
-
Functional multiplexing configuration
-
MPU level 2 interrupt handler
-
MPUIO (the output register (OUTPUT_REG)
-
Input/output control register (IO_CNTL))
-
MCSI (the main parameters register ( MAIN_PARAMETERS__REG))
DPLL registers are reset by all the resets, both hardware and software
The OMAP5910 device global reset sequence with the behavior of the
FLASH.RP pin is shown in Figure 15–15.