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UM10601
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2012. All rights reserved.
Preliminary user manual
Rev. 1.0 — 7 November 2012
196 of 313
NXP Semiconductors
UM10601
Chapter 16: LPC800 I2C-bus interface
16.6.6 I2C Clock Divider register
The CLKDIV register divides down the Peripheral Clock (PCLK) to produce the I
2
C
function clock that is used to time various aspects of the I
2
C interface. The I
2
C function
clock is used for some internal operations in the I
2
C block and to generate the timing
required by the I
2
C bus specification, some of which are user configured in the MSTTIME
register for Master operation and the SLVTIME register for Slave operation.
Section 16.7.1.1 “Rate calculations”
for details on bus rate setup.
16.6.7 I2C Interrupt Status register
The INTSTAT register provides register provides a view of those interrupt flags that are
currently enabled. This can simplify software handling of interrupts. See
detailed descriptions of the interrupt flags.
Table 176. time-out register (TIMEOUT, address 0x4005 0010) bit description
Bit
Symbol
Description
Reset
value
3:0
TOMIN
Time-out time value, bottom four bits. These are hard-wired to 0xF.
This gives a minimum time-out of 16 I
2
C function clocks and also a
time-out resolution of 16 I
2
C function clocks.
0xF
15:4
TO
Time-out time value. Specifies the time-out interval value in increments
of 16 I
2
C function clocks, as defined by the CLKDIV register. To change
this value while I
2
C is in operation, disable all time-outs, write a new
value to TIMEOUT, then re-enable time-outs.
0x000 = A time-out will occur after 16 counts of the I
2
C function clock.
0x001 = A time-out will occur after 32 counts of the I
2
C function clock.
...
0xFFF = A time-out will occur after 65,536 counts of the I
2
C function
clock.
0xFFF
31:16 -
Reserved. Read value is undefined, only zero should be written.
NA
Table 177. I
2
C Clock Divider register (DIV, address 0x4005 0014) bit description
Bit
Symbol
Description
Reset
value
15:0
DIVVAL This field controls how the clock (PCLK) is used by the I
2
C functions
that need an internal clock in order to operate.
0x0000 = PCLK is used directly by the I
2
C function.
0x0001 = PCLK is divided by 2 before use by the I
2
C function.
0x0002 = PCLK is divided by 3 before use by the I
2
C function.
...
0xFFFF = PCLK is divided by 65,536 before use by the I
2
C function.
0
31:16 -
Reserved. Read value is undefined, only zero should be written.
NA