UM10360 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2013. All rights reserved.
User manual Rev. 3 — 19 December 2013 439 of 841
NXP Semiconductors
UM10360
Chapter 19: LPC176x/5x I2C0/1/2
via the I
2
C Clock Control Registers. See the description of the I2CSCLL and I2CSCLH
registers for details. The output clock pulses have a duty cycle as programmed unless the
bus is synchronizing with other SCL clock sources as described above.
19.7.8 Timing and control
The timing and control logic generates the timing and control signals for serial byte
handling. This logic block provides the shift pulses for I2DAT, enables the comparator,
generates and detects START and STOP conditions, receives and transmits acknowledge
bits, controls the master and slave modes, contains interrupt request logic, and monitors
the I
2
C-bus status.
19.7.9 Control register, I2CONSET and I2CONCLR
The I
2
C control register contains bits used to control the following I
2
C block functions: start
and restart of a serial transfer, termination of a serial transfer, bit rate, address recognition,
and acknowledgment.
The contents of the I
2
C control register may be read as I2CONSET. Writing to I2CONSET
will set bits in the I
2
C control register that correspond to ones in the value written.
Conversely, writing to I2CONCLR will clear bits in the I
2
C control register that correspond
to ones in the value written.
19.7.10 Status decoder and status register
The status decoder takes all of the internal status bits and compresses them into a 5-bit
code. This code is unique for each I
2
C-bus status. The 5-bit code may be used to
generate vector addresses for fast processing of the various service routines. Each
service routine processes a particular bus status. There are 26 possible bus states if all
four modes of the I
2
C block are used. The 5-bit status code is latched into the five most
significant bits of the status register when the serial interrupt flag is set (by hardware) and
remains stable until the interrupt flag is cleared by software. The three least significant bits
of the status register are always zero. If the status code is used as a vector to service
routines, then the routines are displaced by eight address locations. Eight bytes of code is
sufficient for most of the service routines (see the software example in this section).
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