NXP Semiconductors Kinetis KE1xZ256, Reference Manual

Page: 523 / 1325

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 22-19. Host reads response from target via SPI
22.5.3 UART Peripheral
The Kinetis Bootloader integrates an autobaud detection algorithm for the UART
peripheral, thereby providing flexible baud rate choices.
Autobaud feature: If UARTn is used to connect to the bootloader, 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 bootloader detects the ping packet
(0x5A 0xA6) on UARTn_RX, the bootloader firmware executes the autobaud sequence.
If the baudrate is successfully detected, then the bootloader 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 Bootloader then enters a loop,
waiting for bootloader 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
Chapter 22 Kinetis ROM Bootloader
Kinetis KE1xZ256 Sub-Family Reference Manual, Rev. 3, 07/2018
NXP Semiconductors 523