UM10413
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User manual
Rev. 1 — 16 December 2011
125 of 268
NXP Semiconductors
UM10413
MPT612 User manual
STO
is the Stop flag. Setting this bit causes the I
2
C interface to transmit a Stop condition
in master mode, or recover from an error condition in slave mode. When STO is logic 1 in
master mode, a Stop condition is transmitted on the I
2
C-bus. When the bus detects the
Stop condition, STO is cleared automatically.
In slave mode, setting this bit causes recovery from an error condition. In this case, no
Stop condition is transmitted to the bus. The hardware behaves as if a Stop condition is
received and it switches to “not addressed” slave receiver mode. The STO flag is cleared
by hardware automatically.
SI
is the I
2
C Interrupt flag. This bit is set when the I
2
C state changes. However, entering
state F8 does not set SI since there is nothing for an interrupt service routine to do in that
case.
While SI is set, the LOW period of the serial clock on the SCL line is stretched, and the
serial transfer is suspended. When SCL is HIGH, it is unaffected by the state of the SI flag.
SI must be reset by software, by writing a logic 1 to bit SIC in register I2CONCLR.
AA
is the Assert Acknowledge flag. When set to logic 1, an acknowledge (LOW level to
SDA) is returned during the acknowledge clock pulse on the SCL line in the following
situations:
•
The address in the slave address register is received
•
The general call address is received while the general call bit (GC) in I2ADR is set
•
A data byte is received while the I
2
C is in the master receiver mode
•
A data byte is received while the I
2
C is in the addressed slave receiver mode
Bit AA can be cleared by writing logic 1 to bit AAC in register I2CONCLR. When AA is
logic 0, a not acknowledge (HIGH level to SDA) is returned during the acknowledge clock
pulse on the SCL line in the following situations:
•
A data byte is received while the I
2
C is in the master receiver mode
•
A data byte is received while the I
2
C is in the addressed slave receiver mode
16.7.2 I
2
C Control clear register (I2CONCLR: I2C0, I2C0CONCLR - 0xE001 C018
and I2C1, I2C1CONCLR - 0xE005 C018)
The I2CONCLR registers control clearing of bits in register I2CON that controls operation
of the I
2
C interface. Writing a logic 1 to a bit in this register causes the corresponding bit in
the I
2
C control register to be cleared. Writing a logic 0 has no effect.
Table 123. I
2
C Control set register (I2CONCLR: I2C0, I2C0CONCLR - address 0xE001 C018
and I2C1, I2C1CONCLR - address 0xE005 C018) bit description
Bit Symbol
Description
Reset
value
1:0 -
reserved, user software must not write logic 1s to reserved bits; value
read from a reserved bit is not defined
n/a
2
AAC
assert acknowledge clear bit
3
SIC
I
2
C interrupt clear bit
0
4
-
reserved, user software must not write logic 1s to reserved bits; value
read from a reserved bit is not defined
n/a