UM10503
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© NXP B.V. 2012. All rights reserved.
User manual
Rev. 1.3 — 6 July 2012
1120 of 1269
NXP Semiconductors
UM10503
Chapter 43: LPC43xx I2C-bus interface
Although the DATA_BUFFER register is primarily intended for use in monitor mode with
the ENA_SCL bit = ‘0’, it will be available for reading at any time under any mode of
operation.
43.7.10 I
2
C Mask registers
The four mask registers each contain seven active bits (7:1). Any bit in these registers
which is set to ‘1’ will cause an automatic compare on the corresponding bit of the
received address when it is compared to the ADRn register associated with that mask
register. In other words, bits in an ADRn register which are masked are not taken into
account in determining an address match.
On reset, all mask register bits are cleared to ‘0’.
The mask register has no effect on comparison to the General Call address (“0000000”).
Bits(31:8) and bit(0) of the mask registers are unused and should not be written to. These
bits will always read back as zeros.
When an address-match interrupt occurs, the processor will have to read the data register
(DAT) to determine what the received address was that actually caused the match.
43.8 I
2
C operating modes
In a given application, the I
2
C block may operate as a master, a slave, or both. In the slave
mode, the I
2
C hardware looks for any one of its four slave addresses and the General Call
address. If one of these addresses is detected, an interrupt is requested. If the processor
wishes to become the bus master, the hardware waits until the bus is free before the
master mode is entered so that a possible slave operation is not interrupted. If bus
arbitration is lost in the master mode, the I
2
C block switches to the slave mode
immediately and can detect its own slave address in the same serial transfer.
Table 992. I
2
C Data buffer register (DATA_BUFFER - address 0x400A 102C (I2C0) and
0x400E 002C (I2C1)) bit description
Bit
Symbol Description
Reset value
7:0
Data
This register holds contents of the 8 MSBs of the DAT shift
register.
0
31:8
-
Reserved. The value read from a reserved bit is not defined.
-
Table 993. I
2
C Mask registers (MASK - address 0x400A 1030 (MASK0) to 0x400A 103C
(MASK3) (I2C0) and 0x400E 0030 (MASK0) to 0x400E 003C (MASK3) (I2C1)) bit
description
Bit
Symbol
Description
Reset value
0
-
Reserved. User software should not write ones to reserved bits.
This bit reads always back as 0.
0
7:1
MASK
Mask bits.
0x00
31:8 -
Reserved. The value read from a reserved bit is not defined.
-