• Bus idle time is always (MCCR0[CLKLO] + 1) multiplied by the prescaler. This is
extended by the time it takes to detect external SDA rising edge.
• START or repeated START hold time is equal to (MCCR0/1[SETHOLD] + 1)
multiplied by the prescaler.
• START, or repeated START, or STOP setup time is equal to
(MCCR0/1[SETHOLD] + 1) multiplied by the prescaler. This is extended by the
time it takes to detect external SCL rising edge.
• SCL low time (before clock stretching) is equal to (MCCR0/1[CLKLO] + 1)
multiplied by the prescaler.
• SCL high time is equal to (MCCR0/1[CLKHI] + 1) multiplied by the prescaler. This
is extended by the time it takes to detect external SCL rising edge.
• SDA output delay is equal to (MCCR0/1[DATAVD] + 1) multiplied by the
prescaler.
The time taken to detect an external rising edge depends on a number of factors including
the bus loading and external pull-up resistor sizing. The minimum delay equals two plus
the pin input digital filter setting (which are configured separately for SCL and SDA),
divided by the prescaler (since the pin input digital filters are not affected by the prescaler
setting).
The following timing restrictions must be enforced to avoid unexpected START or STOP
conditions on the I2C bus or unexpected START or STOP conditions detected by the
LPI2C master. They can be summarized as SDA cannot change when SCL is high
outside of a transmitted (repeated) START or STOP condition.
Table 45-3. Timing Parameters
Timing Parameter
Minimum
Maximum
Comment
CLKLO
0x03
-
CLKLO must also be greater
than delay through the SCL
filter.
CLKHI
0x01
-
SETHOLD
0x02
-
DATAVD
0x01
CLKLO - [(2) / (2 ^
PRESCALER)]
DATAVD must be less than
CLKLO minus delay through
the SDA filter.
FILTSCL
0x00
[CLKLO × (2 ^ PRESCALER)]
- 3
FILTSDA
FILTSCL
[CLKLO × (2 ^ PRESCALER)]
- 3
Does not apply if
compensating for board level
skew between SCL and SDA.
BUSIDLE
(CLKLO+2) × 2
-
Must also be greater than
CLKHI+1.
Chapter 45 Low Power Inter-Integrated Circuit (LPI2C)
Kinetis KE1xZ256 Sub-Family Reference Manual, Rev. 3, 07/2018
NXP Semiconductors
1165
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