UM11029
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User manual
Rev. 1.0 — 16 June 2017
323 of 515
NXP Semiconductors
UM11029
Chapter 18: LPC84x SPI0/1
18.7.2 Frame delays
Several delays can be specified for SPI frames. These include:
•
Pre_delay: delay after SSEL is asserted before data clocking begins
•
Post_delay: delay at the end of a data frame before SSEL is de-asserted
•
Frame_delay: delay between data frames when SSEL is not de-asserted
•
Transfer_delay: minimum duration of SSEL in the de-asserted state between
transfers
18.7.2.1 Pre_delay and Post_delay
Pre_delay and Post_delay are illustrated by the examples in
. The Pre_delay
value controls the amount of time between SSEL being asserted and the beginning of the
subsequent data frame. The Post_delay value controls the amount of time between the
end of a data frame and the de-assertion of SSEL.
Fig 30. Pre_delay and Post_delay
Pre- and post -delay : CPHA = 0, Pre_delay = 2, Post_delay = 1
Mode 2 (CPOL = 1) SCK
MISO
MOSI
SSEL
MSB
MSB
LSB
LSB
Pre_delay
Post_delay
Mode 0 (CPOL = 0) SCK
Pre- and post -delay : CPHA = 1, Pre_delay = 2, Post_delay = 1
Mode 3 (CPOL = 1) SCK
SSEL
Pre_delay
Post_delay
Mode 1 (CPOL = 0) SCK
Data frame
Data frame
MSB
LSB
MSB
LSB