pub const CMD19: Command;Expand description
CMD19 (SD): SEND_TUNING_BLOCK — request a 64-byte tuning pattern.
Used by SD UHS-I (SDR50 / SDR104). Response is R1, immediately followed by a 64-byte data phase the host samples to find a working clock phase. Tuning is iterated up to 40 times by the host controller; the protocol layer just issues this command.