Voltage Switching - Altera cyclone V Technical Reference

cv_5v4
2016.10.28
After the Cortex-A9 MPCore CPU boots, it can deassert the reset signal by clearing the appropriate bits in
the reset manager's corresponding reset register. For details about reset registers, refer to "Module Reset
Signals".
Related Information
Module Reset Signals

Voltage Switching

This section describes the general steps to switch voltage level.
The SD/MMC cards support various operating voltages, for example 1.8V and 3.3V. If you have a card
which is at 1.8V and you eject it and replace it with another card, which is 3.3V, then voltage switching is
required.
In order to have the right voltage level to power the card, separate devices on the board are required:
voltage translation transceiver and power regulator/supply. When the software is aware that voltage
switching is needed, it notifies the power regulator that it needs to supply another voltage level to the card
(switching between 1.8V and 3.3V).
Many SD cards have an option to signal at 1.8 or 3.3 V, however the initial power-up voltage requirement
is 3.3V. To support these different voltage requirements, external transceivers are needed.
The general steps to switch the voltage level requires you to use a SD/MMC voltage-translation transceiver
in between the HPS and the SD/MMC card.
SD/MMC Controller
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Voltage Switching
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