I2Cx_SMB field descriptions
Field
Description
7
FACK
Fast NACK/ACK Enable
For SMBus packet error checking, the CPU must be able to issue an ACK or NACK according to the result
of receiving data byte.
0
An ACK or NACK is sent on the following receiving data byte
1
Writing 0 to TXAK after receiving a data byte generates an ACK. Writing 1 to TXAK after receiving a
data byte generates a NACK.
6
ALERTEN
SMBus Alert Response Address Enable
Enables or disables SMBus alert response address matching.
NOTE: After the host responds to a device that used the alert response address, you must use software
to put the device's address on the bus. The alert protocol is described in the SMBus specification.
0
SMBus alert response address matching is disabled
1
SMBus alert response address matching is enabled
5
SIICAEN
Second I2C Address Enable
Enables or disables SMBus device default address.
0
I2C address register 2 matching is disabled
1
I2C address register 2 matching is enabled
4
TCKSEL
Timeout Counter Clock Select
Selects the clock source of the timeout counter.
0
Timeout counter counts at the frequency of the I2C module clock / 64
1
Timeout counter counts at the frequency of the I2C module clock
3
SLTF
SCL Low Timeout Flag
This bit is set when the SLT register (consisting of the SLTH and SLTL registers) is loaded with a non-zero
value (LoValue) and an SCL low timeout occurs. Software clears this bit by writing a logic 1 to it.
NOTE: The low timeout function is disabled when the SLT register's value is 0.
0
No low timeout occurs
1
Low timeout occurs
2
SHTF1
SCL High Timeout Flag 1
This read-only bit sets when SCL and SDA are held high more than clock × LoValue / 512, which indicates
the bus is free. This bit is cleared automatically.
0
No SCL high and SDA high timeout occurs
1
SCL high and SDA high timeout occurs
1
SHTF2
SCL High Timeout Flag 2
This bit sets when SCL is held high and SDA is held low more than clock × LoValue / 512. Software clears
this bit by writing 1 to it.
0
No SCL high and SDA low timeout occurs
1
SCL high and SDA low timeout occurs
Table continues on the next page...
Memory map/register definition
K22F Sub-Family Reference Manual , Rev. 3, 7/2014
1108
Freescale Semiconductor, Inc.