Fetch ACK
No
Yes
No
Next action
No
Process NAK
Yes
Report an error
No
Yes
No
maximum
Report a
timeout error
Yes
0x5A
received?
0xA2
received?
0xA1
received?
Send 0x00 to
shift out 1 byte
from target
Send 0x00 to
shift out 1 byte
from target
Reached
retries?
Figure 13-22. Host reads ACK from target via SPI
Fetch Response
Yes
Yes
out payload length
part from target
(2 bytes)
out CRC checksum
from target
Payload length
less than supported
length?
Yes
out payload data
from target
No
Set payload length
to maximum
supported length
No
No
maximum
Report a timeout
error (End)
Yes
End
No
(2 bytes)
0x5A
received?
0xA4
received?
Reached
retries?
Send 0x00 to
shift out 1 byte
from target
Send 0x00 to
shift out 1 byte
from target
Write 0x00s to shift
Write 0x00s to shift
Write 0x00s to shift
Figure 13-23. Host reads response from target via SPI
13.4.3 UART Peripheral
The Kinetis Flashloader integrates an autobaud detection algorithm for the UART
peripheral, thereby providing flexible baud rate choices.
Peripherals Supported
K22F Sub-Family Reference Manual , Rev. 3, 7/2014
318
Freescale Semiconductor, Inc.