Inter-Integrated Circuit Peripherals
UG0331 User Guide Revision 15.0
551
15.4.1
Control Register
The following table describes the Control register used for configuring the I
2
C peripherals.
Table 521 •
Control Register (CTRL)
Bit
Number Name R/W
Reset
Value
Description
7
CR2
R/W 0
Clock rate bit 2; refer to bit 0.
6
ENS1 R/W 0
Enable bit. When ENS1 = 0, the SDA and SCL outputs are in a high impedance
and SDA and SCL input signals are ignored. When ENS1 = 1, the I
2
C is
enabled.
5
STA
R/W 0
The Start flag. When STA = 1, the I
2
C peripheral checks the status of the serial
bus and generates a START condition, if the bus is free. STA bit is
automatically cleared after START condition has been generated.
4
STO
R/W 0
The Stop flag. When STO = 1 and the I
2
C is in Master mode, a STOP condition
is transmitted to the serial bus. STO bit is automatically cleared after STOP
condition has been generated.
3
SI
R/W 0
The SI flag. The SI flag is set by the I
2
C whenever there is a serviceable
change in the Status register. Once the register is updated, the SI bit must be
cleared by software.
The SI bit is directly readable through the APB INTERRUPT signal.
2
AA
R/W 0
The assert acknowledge flag.
When AA = 1, an acknowledge is returned when:
– The own slave address is received
– The general call address is received when the GC bit in the address register
is set
– A data byte is received when the core is in the Master-receiver mode
– A data byte is received when the core is in the Slave-receiver mode.
When AA = 0, a not acknowledge is returned when:
– A data byte is received while the core is in Master-receiver mode
– A data byte is received when I
2
C peripheral is in Slave-receiver mode
1
CR1
R/W 0
Serial clock rate bit 1; refer to bit 0
0
CR0
R/W 0
Serial clock rate bit 0. Clock rate is defined in
BCLK is synchronized to PCLK and hence must be PCLKFREQ/2 or less.
Table 522 •
Clock Rate (CR)
CR2
CR1
CR0
SCL Frequency
0
0
0
PCLK frequency/256
0
0
1
PCLK frequency/224
0
1
0
PCLK frequency/192
0
1
1
PCLK frequency/160
1
0
0
PCLK frequency/960
1
0
1
PCLK frequency/120
1
1
0
PCLK frequency/60
1
1
1
BCLK frequency/8
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