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UM10375
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© NXP B.V. 2011. All rights reserved.
User manual
Rev. 3 — 14 June 2011
213 of 368
NXP Semiconductors
UM10375
Chapter 13: LPC13xx I2C-bus controller
Any of these registers which contain the bit 00x will be disabled and will not match any
address on the bus. The slave address register will be cleared to this disabled state on
reset. See also
13.8.5 I
2
C SCL HIGH and LOW duty cycle registers (I2C0SCLH - 0x4000 0010
and I2C0SCLL- 0x4000 0014)
13.8.5.1 Selecting the appropriate I
2
C data rate and duty cycle
Software must set values for the registers I2SCLH and I2SCLL to select the appropriate
data rate and duty cycle. I2SCLH defines the number of I2C_PCLK cycles for the SCL
HIGH time, I2SCLL 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 I2SCLL and I2SCLH 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 I2SCLL and
I2SCLH values.
Table 220. I
2
C Slave Address register 0 (I2C0ADR0- 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 221. I
2
C SCL HIGH Duty Cycle register (I2C0SCLH - 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 222. I
2
C SCL Low duty cycle register (I2C0SCLL - 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
I2CSCLH
I2CSCLL
+
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