NXP Semiconductors K22F series, Reference Manual, Page: 332 / 1407

Autobaud feature: If UARTn is used to connect to the flashloader, then the UARTn_RX
pin must be kept high and not left floating during the detection phase in order to comply
with the autobaud detection algorithm. After the flashloader detects the ping packet
(0x5A 0xA6) on UARTn_RX, the flashloader firmware executes the autobaud sequence.
If the baudrate is successfully detected, then the flashloader will send a ping packet
response [(0x5A 0xA7), protocol version (4 bytes), protocol version options (2 bytes) and
crc16 (2 bytes)] at the detected baudrate. The Kinetis Flashloader then enters a loop,
waiting for flashloader commands via the UART peripheral.
NOTE
• The autobaud feature requires a ping packet with a higher
accuracy (+/-3%), or the ping packet will be ignored as
noise.
• The data bytes of the ping packet must be sent continuously
(with no more than 80 ms between bytes) in a fixed UART
transmission mode (8-bit data, no parity bit and 1 stop bit).
If the bytes of the ping packet are sent one-by-one with
more than 80 ms delay between them, then the autobaud
detection algorithm may calculate an incorrect baud rate. In
this case, the autobaud detection state machine should be
reset.
Supported baud rates: The baud rate is closely related to the MCU core and system
clock frequencies. Typical baud rates supported are 9600, 19200, 38400, 57600, and
115200.
Packet transfer: After autobaud detection succeeds, flashloader communications can
take place over the UART peripheral. The following flow charts show:
• How the host detects an ACK from the target
• How the host detects a ping response from the target
• How the host detects a command response from the target
Peripherals Supported
K22F Sub-Family Reference Manual, Rev. 4, 08/2016
332 NXP Semiconductors