Function cmd53 

pub fn cmd53(
    write: bool,
    function: u8,
    block_mode: bool,
    addr: u32,
    op_code: bool,
    count: u16,
) -> Command

CMD53: IO_RW_EXTENDED

addr is a 17-bit SDIO register address (bits 25:9 of the command argument). count is a 9-bit byte/block count (bits 8:0).