46.4.6.6 Timeout interrupt in SMBus
When the IICIE bit is set, the I2C module asserts a timeout interrupt (outputs SLTF and
SHTF2) upon detection of any of the mentioned timeout conditions, with one exception.
The SCL high and SDA high TIMEOUT mechanism must not be used to influence the
timeout interrupt output, because this timeout indicates an idle condition on the bus.
SHTF1 rises when it matches the SCL high and SDA high TIMEOUT and falls
automatically just to indicate the bus status. The SHTF2's timeout period is the same as
that of SHTF1, which is short compared to that of SLTF, so another control bit,
SHTF2IE, is added to enable or disable it.
46.4.7
Programmable input glitch filter
An I2C glitch filter has been added outside legacy I2C modules but within the I2C
package. This filter can absorb glitches on the I2C clock and data lines for the I2C
module.
The width of the glitch to absorb can be specified in terms of the number of (half) I2C
module clock cycles. A single Programmable Input Glitch Filter control register is
provided. Effectively, any down-up-down or up-down-up transition on the data line that
occurs within the number of clock cycles programmed in this register is ignored by the
I2C module. The programmer must specify the size of the glitch (in terms of I2C module
clock cycles) for the filter to absorb and not pass.
SCL, SDA
external signals
DFF
Noise
suppress
circuits
SCL, SDA
internal signals
DFF DFF DFF
Figure 46-5. Programmable input glitch filter diagram
46.4.8
Address matching wake-up
When a primary, range, or general call address match occurs when the I2C module is in
slave receive mode, the MCU wakes from a low power mode where no peripheral bus is
running.
After the address matching IAAS bit is set, an interrupt is sent at the end of address
matching to wake the core.
Chapter 46 Inter-Integrated Circuit (I2C)
K22F Sub-Family Reference Manual, Rev. 4, 08/2016
NXP Semiconductors 1209
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