Shortest time required UART- UART transfer of 32 Byte block
Time required would be 32 bytes * 12 bits/byte divided by the baud rate.  (1 start bit + 8 data bits + 1 parity bit + 2 stop bits = 12 bits).  The baud rate is the 'bit clock' that determines how long the bits are.  A standard baud rate is 115200 bits per second.  This may or may not be the baud rate you're using.  Other standard baud rates are 2400, 4800, 9600, 19200, and 38400.  If the baud rate is 115200, then the time required to transmit 32 bytes is 32 * 12 / 115200 = 3.33 ms.