UM10413
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User manual
Rev. 1 — 16 December 2011
124 of 268
NXP Semiconductors
UM10413
MPT612 User manual
16.7.1 I
2
C Control set register (I2CONSET: I2C0, I2C0CONSET - 0xE001 C000 and
I2C1, I2C1CONSET - 0xE005 C000)
The I2CONSET registers control setting 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
register I
2
C control to be set. Writing a logic 0 has no effect.
I2EN
I
2
C Interface Enable. When I2EN is logic 1, the I
2
C interface is enabled. I2EN can be
cleared by writing logic 1 to bit I2ENC in register I2CONCLR. When I2EN is logic 0, the
I
2
C interface is disabled.
When I2EN is logic 0, the SDA and SCL input signals are ignored, the I
2
C block is in the
“not addressed” slave state, and bit STO is forced to logic 0.
I2EN must not be used to release the I
2
C-bus temporarily, since when I2EN is reset, the
I
2
C-bus status is lost. The AA flag must be used instead.
STA
is the Start flag. Setting this bit causes the I
2
C interface to enter master mode and
transmit a Start condition or transmit a repeated Start condition if it is already in master
mode.
When STA is logic 1 and the I
2
C interface is not already in master mode, it enters master
mode, checks the bus and generates a Start condition if the bus is free. If the bus is not
free, it waits for a Stop condition (which frees the bus) and generates a Start condition
after a delay of a half-clock period of the internal clock generator. If the I
2
C interface is
already in master mode and data is transmitted or received, it transmits a repeated Start
condition. STA can be set at any time, including when the I
2
C interface is in an addressed
slave mode.
STA can be cleared by writing logic 1 to bit STAC in register I2CONCLR. When STA is
logic 0, no Start condition or repeated Start condition is generated.
If STA and STO are both set, then a Stop condition is transmitted on the I
2
C-bus if the
interface is in master mode, and transmits a Start condition thereafter. If the I
2
C interface
is in slave mode, an internal Stop condition is generated, but is not transmitted on the bus.
Table 122. I
2
C Control set register (I2CONSET: I2C0, I2C0CONSET - address 0xE001 C000
and I2C1, I2C1CONSET - address 0xE005 C000) 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
AA
assert acknowledge flag; see text below
3
SI
I
2
C interrupt flag
0
4
STO
stop flag; see text below
0
5
STA
start flag; see text below
0
6
I2EN
I
2
C interface enable; see text below
0
7
-
reserved, user software must not write logic 1s to reserved bits;
value read from a reserved bit is not defined
n/a