NXP Semiconductors K32 L2A Series, Reference Manual, Page: 297 / 1379

• Processing incoming packet
• Preparing outgoing data
• Received invalid data
The LPSPI bus configuration is:
• Phase = 1; data is sampled on rising edges
• Polarity = 1; idle is high
• MSB is transmitted first
For any transfer where the target does not have actual data to send, the target (slave) is
responsible for ensuring that 0x00 bytes will be returned to the host (master). The host
uses framing packets to identify real data and not "dummy" 0x00 bytes (which do not
have framing packets).
The following flowcharts demonstrate how the host reads a ping response, an ACK and a
command response from target via LPSPI.
Fetch
Ping response
Yes
Yes
End
Report Error
No
No
0x5A
received?
0xA7
received?
Send 0x00 to
shift out 1 byte
from target
Send 0x00 to
shift out 1 byte
from target
Send 0x00s to shift
out leftover bytes
of ping response
Figure 14-24. Host reads ping packet from target via LPSPI
Chapter 14 Kinetis ROM Bootloader
K32 L2A Reference Manual, Rev. 2, 01/2020
NXP Semiconductors 297