Resets; Safe Mode - Altera cyclone V Technical Reference

cv_5v4
2016.10.28
Name
ddr_2x_dqs_clk
ddr_dq_clk
h2f_user2_clock

Resets

Cold Reset
Cold reset places the hardware-managed clocks into safe mode, the software-managed clocks into their
default state, and asynchronously resets all registers in the clock manager.
Related Information

Safe Mode

Warm Reset
Registers in the clock manager control how the clock manager responds to warm reset. Typically, software
places the clock manager into a safe state in order to generate a known set of clocks for the ROM code to
boot the system. The behavior of the system on warm reset as a whole, including how the FPGA fabric,
boot code, and debug systems are configured to behave, must be carefully considered when choosing how
the clock manager responds to warm reset.
The reset manager can request that the clock manager go into safe mode as part of the reset manager's
warm reset sequence. Before asserting safe mode to the clock manager, the reset manager ensures that the
reset signal is asserted to all modules that receive warm reset.
Related Information
Reset Manager
For more information, refer to "Reset Sequencing" in the Reset Manager chapter.
Safe Mode
Safe mode is enabled in the HPS by the assertion of a safe mode request from the reset manager or by a
cold reset. Assertion of the safe mode request from the reset manager sets the safe mode bit in the clock
manager control register. No other control register bits are affected by the safe mode request from the reset
manager.
When safe mode is enabled, the main PLL hardware-managed clocks (C0-C2) are bypassed to
clock and are directly generated from
which control clock behavior, are not changed. However, the hardware bypasses these settings and uses
safe, default settings.
Clock Manager
Send Feedback
SDRAM PLL C1
SDRAM PLL C2
SDRAM PLL C5
on page 2-17
on page 3-1
Frequency
. While in safe mode, clock manager register settings,
osc1_clk
Resets
Constraints and Notes
Clock for PHY
Clock for PHY
Auxiliary user clock to the FPGA
fabric
Altera Corporation
2-17
osc1_clk