valdez151
Newbie level 1
Hi,
could you help me with understanding part of SD card specification. I'm not sure what and how to change to 1.8V. If I want UHS mode, card should be still supplied with 3.3V but CLK, CMD and DATA lines should have 1.8V signalling? Or card should also be supplied with 1.8V ? Secondly, how to switch signalling from 3.3V to 1.8V on Spartan 3 during it's work, initialization? Is that possible without external hardware or I need some voltage level translator? It is the part of specification:
"As higher bus speed requires low level signaling, UHS-I adopts 1.8V signaling level for SDR50, DDR50
and SDR104 modes. Still card is supplied with 3.3V by the host and 1.8V signaling level for SDCLK,
CMD and DAT[3:0] lines is converted from 3.3V power line. To avoid voltage mismatch between host
and card, signaling level is changed by voltage switch sequence at the initialization. The host and card
communicate using ACMD41 whether host and card support 1.8V signaling mode. Support of 1.8V
signaling both host and card means UHS-I can be used. CMD11 invokes the voltage switch sequence.
The card enters UHS-I mode and card input and output timings are changed (SDR12 in default) when
the voltage switch sequence is completed successfully."
could you help me with understanding part of SD card specification. I'm not sure what and how to change to 1.8V. If I want UHS mode, card should be still supplied with 3.3V but CLK, CMD and DATA lines should have 1.8V signalling? Or card should also be supplied with 1.8V ? Secondly, how to switch signalling from 3.3V to 1.8V on Spartan 3 during it's work, initialization? Is that possible without external hardware or I need some voltage level translator? It is the part of specification:
"As higher bus speed requires low level signaling, UHS-I adopts 1.8V signaling level for SDR50, DDR50
and SDR104 modes. Still card is supplied with 3.3V by the host and 1.8V signaling level for SDCLK,
CMD and DAT[3:0] lines is converted from 3.3V power line. To avoid voltage mismatch between host
and card, signaling level is changed by voltage switch sequence at the initialization. The host and card
communicate using ACMD41 whether host and card support 1.8V signaling mode. Support of 1.8V
signaling both host and card means UHS-I can be used. CMD11 invokes the voltage switch sequence.
The card enters UHS-I mode and card input and output timings are changed (SDR12 in default) when
the voltage switch sequence is completed successfully."