UM10503
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© NXP B.V. 2012. All rights reserved.
User manual
Rev. 1.3 — 6 July 2012
1121 of 1269
NXP Semiconductors
UM10503
Chapter 43: LPC43xx I2C-bus interface
43.8.1 Master Transmitter mode
In this mode data is transmitted from master to slave. Before the master transmitter mode
can be entered, the CONSET register must be initialized as shown in
must be set to 1 to enable the I
2
C function. If the AA bit is 0, the I
2
C interface will not
acknowledge any address when another device is master of the bus, so it can not enter
slave mode. The STA, STO and SI bits must be 0. The SI Bit is cleared by writing 1 to the
SIC bit in the CONCLR register. The STA bit should be cleared after writing the slave
address.
The first byte transmitted contains the slave address of the receiving device (7 bits) and
the data direction bit. In this mode the data direction bit (R/W) should be 0 which means
Write. The first byte transmitted contains the slave address and Write bit. Data is
transmitted 8 bits at a time. After each byte is transmitted, an acknowledge bit is received.
START and STOP conditions are output to indicate the beginning and the end of a serial
transfer.
The I
2
C interface will enter master transmitter mode when software sets the STA bit. The
I
2
C logic will send the START condition as soon as the bus is free. After the START
condition is transmitted, the SI bit is set, and the status code in the STAT register is 0x08.
This status code is used to vector to a state service routine which will load the slave
address and Write bit to the DAT register, and then clear the SI bit. SI is cleared by writing
a 1 to the SIC bit in the CONCLR register.
When the slave address and R/W bit have been transmitted and an acknowledgment bit
has been received, the SI bit is set again, and the possible status codes now are 0x18,
0x20, or 0x38 for the master mode, or 0x68, 0x78, or 0xB0 if the slave mode was enabled
(by setting AA to 1). The appropriate actions to be taken for each of these status codes
are shown in
.
Table 994. CONSET used to configure Master mode
Bit
7
6
5
4
3
2
1
0
Symbol
-
I2EN
STA
STO
SI
AA
-
-
Value
-
1
0
0
0
0
-
-
Fig 159. Format in the Master Transmitter mode
A = Acknowledge (SDA low)
A = Not acknowledge (SDA high)
S = START condition
P = STOP condition
S
SLAVE ADDRESS
RW=0
A
DATA
A
A/A
P
from Master to Slave
from Slave to Master
DATA
n bytes data transmitted
