UM10462
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User manual
Rev. 5.5 — 21 December 2016
296 of 523
NXP Semiconductors
UM10462
Chapter 14: LPC11U3x/2x/1x I2C-bus controller
14.7.4 I
2
C Slave Address register 0 (ADR0)
This register is readable and writable and are only used when an I
2
C interface is set to
slave mode. In master mode, this register has no effect. The LSB of the ADR register is
the General Call bit. When this bit is set, the General Call address (0x00) is recognized.
If this register contains 0x00, the I
2
C will not acknowledge any address on the bus. All four
registers (ADR0 to ADR3) will be cleared to this disabled state on reset. See also
14.7.5 I
2
C SCL HIGH and LOW duty cycle registers (SCLH and SCLL)
14.7.5.1 Selecting the appropriate I
2
C data rate and duty cycle
Software must set values for the registers SCLH and SCLL to select the appropriate data
rate and duty cycle. SCLH defines the number of I2C_PCLK cycles for the SCL HIGH
time, SCLL defines the number of I2C_PCLK cycles for the SCL low time. The frequency
is determined by the following formula (I2C_PCLK is the frequency of the peripheral I2C
clock):
(4)
The values for SCLL and SCLH must ensure that the data rate is in the appropriate I
2
C
data rate range. Each register value must be greater than or equal to 4.
gives
some examples of I
2
C-bus rates based on I2C_PCLK frequency and SCLL and SCLH
values.
Table 274. I
2
C Slave Address register 0 (ADR0- 0x4000 000C) bit description
Bit
Symbol
Description
Reset value
0
GC
General Call enable bit.
0
7:1
Address
The I
2
C device address for slave mode.
0x00
31:8 -
Reserved. The value read from a reserved bit is not defined.
-
Table 275. I
2
C SCL HIGH Duty Cycle register (SCLH - address 0x4000 0010) bit description
Bit
Symbol
Description
Reset value
15:0
SCLH
Count for SCL HIGH time period selection.
0x0004
31:16
-
Reserved. The value read from a reserved bit is not defined.
-
Table 276. I
2
C SCL Low duty cycle register (SCLL - 0x4000 0014) bit description
Bit
Symbol
Description
Reset value
15:0
SCLL
Count for SCL low time period selection.
0x0004
31:16
-
Reserved. The value read from a reserved bit is not defined.
-
I2C
bitfrequency
I2CPCLK
SCLH
SCLL
+
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